If you hear a Jockey nearby, try to position yourself so that the Jockey targets the survivor near you and pounces on them. Then, you can take him out either with an autoshotgun or a melee attack before the timer runs out. Other weapons can also be used, however these two I mentioned have a very high chance of killing the Jockey before the timer runs out.

Spitter bots will spit at you the second they make line of sight with you and are within combat distance (roughly 850 hammer units; close to the length between the bridge and the stairs leading to the overpass to the gun shop in the second chapter of Dead Center). So your two options are to either have a good enough reaction time to kill a Spitter before she spits, or to kill her when she's out of spitting range. When going with the first option, sound is your best friend; you can use it to anticipate the Spitter's movements, or straight up use it as a guide when trying to wallbang her.

Self-explanatory. Ammo upgrade kits spawn in most, if not all campaigns, especially the L4D2 ones. Best done in singleplayer, as survivor bots are programmed to automatically pick up ammo upgrades.

These barrels spawn only in the Sacrifice campaign. While it is possible to get this achievement in single-player, setting up a Versus match with a friend can drastically speed things up. AFAIK both the initial blast and the fire count as barrel damage, so if the SI dies to either of those, the achievement should pop. Below are two images showcasing the barrels.



If you're playing single-player, try to bait an SI into coming near the barrel before blowing them into orbit. If the survivor bots keep killing the SI before it can die to the barrel, you can kick them via the console.

You need to escape whilst alive for the achievement to count

I recommend either loading up a Mutation that makes the game considerably easier (e.g. Gib Fest, Last Man on Earth, and especially Rocket Dude), or switching the game to Easy difficulty and making sure you're stocked up on ammo, weapons, and supplies, before attempting to cross the bridge. You might have to skip the Tank, if taking him down will take too much of your time. Adrenaline is extremely valuable to have.

The achievement flag is toggled when all survivors reach the escape vehicle and the escape cutscene is triggered. The 3-minute timer starts the second the gate crashes down, and the bridge becomes traversable.

Self-explanatory. Autoshotguns with incendiary rounds can make quick work of a horde in just one or two shots. Alternatively, you can earn this achievement with just a single M16 magazine, if you make sure every shot connects to a common, given that incendiary rounds of any weapon instakill commons in just one shot. You'll probably earn this achievement through regular gameplay anyway.

Foot Lockers appear in the Passing campaign; they contain unlimited amounts of a random item, like molotovs, pills, etc. You can restart the first chapter over and over and keep looting the lockers in the first building (not room) you enter, assuming they appear.

Self-explanatory. Chainsaws appear in all campaigns, but L4D2 campaigns seem to have more of them. You can use bile bombs to create an artificial horde and aggregate commons into one area before mowing them down.

Clowns appear in the Dark Carnival campaign. You can honk a clown's nose by shoving them. Multiple shoves on one clown do count towards the achievement, but do note that they will die after receiving 4 shoves, meaning you'll have to find a new clown.

This achievement requires you to kill at least one common with every melee weapon defined in the achievement. These are the: Fireaxe, Cricket Bat, Crowbar, Guitar, Frying Pan, Machete, Nightstick, and Katana.

You can use Survival maps to easily acquire each of these weapons, as their spawns will be predetermined there. You can use Gold Miners' Survival Guide to read up on the contents of every survival map.

Alternatively, the last 5 melee weapons in the list are almost guaranteed to be found in Dark Carnival, Swamp Fever, Last Stand, Crash Course, and Dead Center/Dark Carnival respectively, while the first three are almost universal to all campaigns.

Throwables, mounted machine guns, and weapons fire from bots do not void the achievement.

The player needs to finish an entire campaign, not just finish the last chapter. Thus, it's best to go with Crash Course, as it's unarguably the shortest map.

The player simply needs to kill at least one of every uncommon infected defined in the achievement. These are the: CEDA Worker (found in Dead Center/The Sacrifice), Construction Worker (found in Hard Rain), Mudman (found in Swamp Fever), and the Clown (found in Dark Carnival)

Mudmen appear mostly in Swamp Fever. Best way to go about this is to chuck a pipe bomb/bile bomb into a body of water and let the infected pile up.

After you find a grenade launcher, look for a bile bomb, or even a pipe bomb. If you have a bile bomb, just throw it in a place where the survivor bots won't reach it (or just kick them), and fire away. If you have a pipe bomb, wait for a horde to spawn, and throw the bomb into a place where the zombies can easily aggregate. You won't have to kick survivor bots for the pipe bomb, as they are programmed to automatically ignore any commons in the vicinity of the bomb.

The achievement description is misleading; the Tank simply needs to be alive for the achievement to trigger.

Adrenaline can be very helpful when attempting this achievement. After a Survivor is incapacitated, make sure the that Tank isn't targeting either of you two, or that it's far enough away for you to be able to revive a Survivor fast enough (hence why Adrenaline can be very helpful).

Not much to say about this one. Aim for the head... Or slightly above it.

Trial and error; wait for a horde to spawn in Dark Carnival and incinerate it. You'll eventually stumble upon a horde with a clown in it, often granting the achievement when ignited.

Simply kill a Hunter in its pouncing state with a shotgun of any type (an autoshotgun is recommended, so that you can unleash a salvo of shots upon the Hunter, instead of just one or two with a pump-action). You can launch the Last Man on Earth mutation to cross common infected out of the picture, leaving you with just special infected.

The free holiday in question must play through an entire campaign, and get to the rescue vehicle alive. Violating either condition will void the achievement.

Free holiday players are hard to come by, but you might stumble upon one by joining random pubs. You can also ask for free holiday players on the game's Steam Community page, or social media.

Automatically unlocked after loading into any server.

Refer to this guide[antifandom.com] (breezewiki link, for official fandom site look up Golden Freeman Achievement on the official Left4Dead wiki.)

In the Barns chapter (chapter 4) of Dark Carnival, there is a Moustachio Strong Man game machine. It's pretty hard to miss, as it's opposite to the bumper car arena.

The player needs to hit the pad in front of the gong with a melee weapon under the effects of adrenaline. This will earn you this achievement and spawn a horde.

Fallen Survivors spawn on the Passing, and in small amounts on the L4D2 versions of No Mercy, Crash Course, and Death Toll. They will run away from the Survivors when spotted, and will drop all of their held loot on death.

They can take quite a beating before they die, so it's recommended to find a Magnum pistol, which can kill them in just two hits. Alternatively, a headshot from any weapon or a hit from a melee weapon will instantly kill them.

Gnome Chompski can be acquired in the second chapter of Dark Carnival. He's locked inside of a cage near a shooting gallery minigame. Racking up 750 points in one run of the game will unlock the cage, allowing Gnome Chompski to be taken.

The gnome will persist between level transitions if it's inside of a saferoom, though the gnome should be kept in one's hands at all times to not lose track of it.

This achievement should be attempted in a public lobby, because survivor bots might not prove to be the best at covering the player. If a Tank has spawned, put the gnome in a safe place before engaging it. During the fourth chapter (the Barns), it's best to toss the gnome over the fence right into the stadium entrance, as this will allow you to proceed through the chapter unhindered.

Self-explanatory. Pick up a melee weapon and go nuts. Do note, that not every weapon can decapitate. Your best bet are sharp melee weapons, with the exception of the Crowbar.

The room is located in the first chapter of the Last Stand. It is relatively close to the beginning of the chapter, as it's behind the first building you encounter after crossing through a tunnel (you'll have to jump down from the balcony to access the back side). The door can only be brought down with a melee weapon (there's a guaranteed spawn near the door itself), and it requires roughly 34 hits to break. Inside there will be a keyboard, that when interacted with, will grant the Golden Freeman achievement along with a golden crowbar (does not differ from a regular crowbar stat-wise)



(Click picture to enlarge)

The achievement requires the player playing as Bill to sacrifice himself at the end of the Sacrifice campaign. Upon doing so, the achievement is awarded to everyone in the lobby.

The jukebox in question can be found in the second and final chapters of the Passing.
Simply keep switching songs, as the achievement requires a specific song out of the entire set to play.

This achievement is earned in the Passing.

There are two ways of going about this in singleplayer. You can either kick your survivor bots and do what the achievement says, or, after activating the generator, wait at the bridge until a Tank spawns. When it does, book it to the car as fast as possible, and the achievement should unlock. This is because all Tank bots die after triggering the ending cutscene, and the achievement actually just checks if your team didn't do any damage.

Attempting this achievement normally is going to be a fruitless endeavour no matter what.

Launch the Last Man on Earth mutation, and wait for a Charger to spawn. Chargers have a very high health pool AND damage resistance while charging, so you'll need to weaken him with a few shots from a firearm. Afterwards, wait for the Charger to charge (or for his charge to regenerate if he has charged already), and try to swing at him mid-charge (if possible, aim at his big arm, since it has a 1.5× damage multiplier).

Alternatively, host a local Versus match and have one of your friends spawn as a Charger, and coordinate the attempt from there.

The Chainsaw does not count towards this achievement. This is one of the achievements that will require gameplay skill from the player. When the Smoker uses his tongue, he fires a projectile that homes in on the player and travels at a fixed speed. Using this, you can calculate the timing required to cut the tongue, as the window is pretty tight (note that when you're close enough to the Smoker, the timing becomes negative; you'll have to swing before the Smoker fires his tongue). The middle of your melee strike animation needs to make contact with the tongue in order to cut it. Doing this, even once, might take a fair amount of practice. Video for reference[files.catbox.moe]

You need to escape whilst alive for the achievement to count

The only reason I'm putting this one into the one-man category is because this exists[files.catbox.moe]. In order to pull this off you'll have to get a melee hit on the witch to wake her up, dodge her first attack, and then hope you have enough time to get in the other three attacks before you get instakilled. All of that assuming the witch doesn't instantly book it to you the second she wakes up, and hovers in place for a bit instead. If you're going to attempt this in singleplayer, make sure to kick all bots.

If you have a sound mind, however, it's best you set up a Chainsaw Massacre mutation with a friend, and mow down the witch with two chainsaws. If the witch is near the beginning safehouse, you can wake her up, and run to the safehouse; if a targeted player enters a safehouse, the witch will begin retreating, and will only attack players that actively block her way. If you manage to get her into the retreating state, you can let the other player wait for the witch to come to them and mow her down.

You need to escape whilst alive for the achievement to count

The Last Stand campaign has a guaranteed shovel at the very start, to the right of your spawn. Thus, you can launch the Last Stand on the Last Man on Earth mutation, and farm Jockey kills.

There's also a custom mutation made specifically for this achievement

You need to escape whilst alive for the achievement to count

CEDA Workers spawn most commonly in Dead Center and The Sacrifice. A good place to farm CEDA Workers is The Port (Sacrifice) in Survival.

Tank rocks have 50 HP, and upon depleting that HP, the rock is destroyed. Note, that tank rocks have a brief period of invulnerability after being thrown, meaning you'll have to put a good amount of distance between yourself and the tank.

The best map for attempting this is probably the Concert in Dark Carnival, as it's got a lot of open space. As for weapons, the AK or the Military Sniper Rifle should be able to destroy a rock in 1-2 hits.

Pretty easy to achieve in Dead Center. Load up the campaign and look for bile bombs. They're common in the first chapter as predefined spawns, and in the second chapter as drops from CEDA Workers.

For the achievement to trigger, the bile bomb has to affect the Tank, that is, give him a purple outline, indicating he's been hit with the bile bomb.

If you prioritise taking defibrillators whenever possible, it's likely you'll get this achievement through regular gameplay. Otherwise, you can launch the Bleed Out mutation on any map and look out for any defibrillators. Deaths are quite common in that mode, so getting a survivor to die shouldn't be a problem.

The bride witch spawns in the first chapter of the Passing.

In order to do this, you'll have to get extremely close up to the witch, and blast her head off when it's as close to you as possible (which is when she'll be standing up). Video for reference[files.catbox.moe]. The wooden pump shotgun is recommended, as it has slightly more damage than the chrome shotgun, though the chrome shotgun has a tighter spread.

Note that you can't kill any Witch, meaning that if you startle one, you can still get the achievement if you can book it to the safehouse fast enough.

An easy way to score this one is to launch the Sugar Mill chapter on the Last Man on Earth mutation on Easy difficulty, and just rush through the level. (or just launch Rocket Dude lol)

For this one, the player needs to score at least 42 points in the Whack-a-Mole game in total. The game is located in the Barns chapter of the Dark Carnival, it's located before the entrance to the barns themselves, and needs to be interacted with to be turned on.

It's recommended to launch this chapter in Survival, so that common infected won't be distracting you.

This achievement includes only the L4D2 campaigns, that is, Dead Center, Dark Carnival, Swamp Fever, Hard Rain, and the Parish.

Undoubtably, good game sense is required for this achievement. Bringing friends is also recommended, as this will make the campaigns much easier, though in the worst case scenario beating all campaigns solo is possible.

Throwables and medical supplies will be extremely valuable, and you should treat them as such; throw molotovs only at the Tank, or into a clumped-up horde coming towards you; use pipe bombs only when you're certain you can't hold off the infected using your weapons alone; use bile bombs EXTREMELY strategically, as they can disable all commons from attacking you for a brief period of time, which can be a godsend during crescendo events or escape sequences. Use pain killers only before crescendo events, escape sequences, or a Tank encounter; treat adrenaline purely as a significant decrease to your interaction time and use it as such, for example when reviving a survivor during a Tank encounter, or pouring large quantities of gas into a generator; use First Aid Kits when you're out of painkillers and are below 40 HP. Keep a mental note of your teammates' status, don't hoard all meds for yourself. If you can get accustomed to the Magnum pistol, it can be a very useful tool, especially when incapacitated. Listen for special infected in order to have the upper hand against them; it is much better to switch your focus off the horde and onto the special instead of having that special pin down, and potentially kill one of your teammates. This might also be a good time to learn: how to deadstop both Hunters[files.catbox.moe] and Jockeys[files.catbox.moe], how to cut a Smoker's tongue mid-air[files.catbox.moe], how to crown a witch[files.catbox.moe], and how to get melee hits on the Tank[files.catbox.moe]. (note, that knowing how to cut a Smoker's tongue [or just good awareness of yourself and your teammates] might be especially useful, given the fact that a Smoker's reaction time is instant on difficulties above Normal)

Dark Carnival is unarguably the hardest one of them all to beat on Expert. It is HIGHLY recommended you try to find a bile bomb in the first chapter; if it doesn't spawn on the highway (two spawn points for the bomb are in the truck and in the campsite before the offramp respectively), reset the campaign. The bile bomb will be realistically your only way to plow through the crescendo event at the stadium gates in the fourth chapter. When approaching the coaster, you can skip the entire crescendo event by doing some precise platforming, as shown[files.catbox.moe]. You can also utilise this clip brush[files.catbox.moe] to skip the whole alarm switch section.

You need to escape whilst alive for the achievement to count

You need to escape whilst alive for the achievement to count

For the achievement to trigger, the Tank must receive damage ONLY from melee weapons. No exceptions.

You can launch the Chainsaw Massacre mutation, and mow down the tank with a team of survivor bots (just make sure none of them get incapacitated, as they'll start using their pistols).

Alternatively, you can utilise melee kiting (read video desc)

Launch the campaign on Easy, and try to get through it as fast as possible. Make sure you're familiar with the map before you attempt this achievement.

It's crucial you launch the campaign on Easy, as this will lower the amount of gas cans required to power the generator back up.

You can also launch the campaign with the Gib Fest mutation, reducing difficulty even further

There are two ways of going about this in singleplayer. One with bots, one without.

If you want to play with bots, I recommend launching the Concert chapter on Easy difficulty and making sure the bots don't wander off stage, that is, target any Spitters and Smokers you hear/see, and decimate any Tank as fast as possible.

If you want to go solo, you can launch the Lone Gunman/Last Man on Earth mutation on Easy difficulty. I'd recommend going solo, as there have been reports of the achievement not triggering when playing with bots, even if they didn't get off the stage.

Keep adrenaline on you at all times and be the first one to revive your teammates, and this achievement should pop up quite quickly. Note that the incap must be natural, that is, you can't friendly fire another player and help them up. Falling off a ledge, however, does count as a natural incapacitation.

Dead Center and the Passing are without a doubt the easiest ones to do this achievement on. If you want, you don't even have to bother with launching them, because you'll have to do the Last Stand on Expert Realism down the line anyway.

You can kill all bots with friendly fire on Expert, then call a vote to switch the difficulty to Easy, and progress the level to the nearest rescue closet. A single survivor spawns inside the closet every minute or so.

The Gib Fest mutation is a perfect match for this achievement, due to the guaranteed M60 alongside infinite ammo, meaning you can hold down the trigger as long as you want.

If you want to do this without using the mutation, you'll have to find an M60 and wait for a horde to spawn; crescendo events are good opportunities to get this achievement.

You need to escape whilst alive for the achievement to count

The impound lot is in the Cemetery chapter of the Parish. It's best to launch this chapter with the Last Man on Earth mutation and proceed through the lot without triggering any alarms. Switching to a melee playstyle can help prevent accidental alarms. Note that incendiary ammunition does not set off car alarms, meaning it can be a good choice to snag an Incendiary Ammo pack on the way.

You need to escape whilst alive for the achievement to count

Start the Swamp chapter of Swamp Fever on Easy difficulty. Get to the airliner, trigger the door, and fortify yourself in the back area of the inside of the plane. This isn't a party achievement, meaning only you can't take damage to get the achievement.

This one you'll have to grind out, if you don't want to use custom maps. If you do, just look up "z-genocidest" in the workshop and some maps should pop up. Here's one I pulled out of my aꜱꜱ after 30 seconds of searching. Do note, that after your farming session is done, make sure to launch any campaign to make sure the data saves.

If you don't want to use custom maps, then with top-ranking amounts of kills in every chapter in a pub, you'll be done with the achievement in roughly 300 hrs of game time. If you want to achieve this faster, you can launch the Stadium chapter of Dark Carnival on Easy, and farm kills in the Stadium Gate crescendo event.

You'll need two other people for this. In the final chapter of the Sacrifice, situate each person near a generator, and coordinate the team to start every generator at once. The timing isn't that tight, so there's a big margin for error.

While this might be possible with a crew of two people, it's highly recommended to have at least two other players with you. Player 1 should stay near the car, aggregating all the cans that players 2 and 3 will be throwing down. Player 1 should be armed with adrenaline before starting to pour the gas in. If all cans have been acquired and thrown down for P1 to collect, players 2 and 3 should start heading for the car.

Note that the tank spawn is dictated by the amount of common infected killed. Thus, it's best to avoid killing them when possible, and a bile bomb can greatly help with that. If you happen to find bile bombs laying around, chuck one into a far-away place so that you get a few seconds of uninterruped gameplay.

It's theoretically possible to do this achievement solo, as the gas requirement in Singleplayer is reduced to just 8 cans, but you'd have to manage your survivor bots, and stop them from killing too many infected.

This one is so unbelievably hard that I'll put TWO skill markers instead of just one. While this MIGHT be possible to do solo with bots if you're a literal god, even 4-man crews often get destroyed by this map on ER.

Make sure everyone's familiar with the map and has good coordination skills before attempting this. All advice I gave on STILL SOMETHING TO PROVE applies to Expert Realism as well, though melee weapons might be more favorable than the Magnum. Defibrillators are often more valuable than a First Aid Kit, so make sure you have just one, no more, no less.

Listening for the sounds of special infected is CRUCIAL to your survival; if you hear a pinning special near your teammate, focus your aim on the teammate, since when they get pinned, you'll already be aiming at the SI, thus minimising the amount of damage they can deal. Tank shredding is also important; have molotovs and gas cans on hand, as fire is extremely helpful when dealing with Tanks.

Make sure you're in as good of a state as you can before closing the saferoom in the first chapter, because you'll be dying in the second one a LOT, so if one of the survivors forgot to heal before closing the door, they'll have to heal on every, single, restart.

If you want to cheese this achievement, that's where Rayman's Mutation Mod comes in (for the mod download, check the Mutations and the Developer Console chapter of this guide), as the mod contains the Gib Fest Realism mutation. So all you need to do is launch this mutation on Expert on the Last Stand, and mow through the entire campaign.

If you want to add more cheese, you can paste this command into the console:
and then type kickloop into the console to start the loop.

The command I just showed you kicks every SI (except for the Tank, as kicking the Tank instantly in the Last Stand softlocks the run), waits for 90 frames, and then repeats itself, which in Layman's terms means it sends all special infected on a paid vacation, leaving you with just commons, and the Tank.

To disable the alias, you can change it's target command to something useless, or restart the game.

Bronze medals are awarded after surviving for 4 minutes on a survival map.

Silver medals are awarded after surviving for 7 minutes on a survival map.

Gold medals are awarded after surviving for 10 minutes on a survival map.

Honestly I don't know how you should go about this one without having an extremely coordinated team. There is another way, though, and it involves the Atrium, a friend, and a grenade launcher[files.catbox.moe]. Keep in mind, that even after you get on top of the elevator, you'll still have to fight against Tanks and Spitters, and perhaps the occasional Smoker.

Alternatively, you can check out this much simpler method suggested by Pookatank, which should also allow you to get Beat the Rush

This achievement is quite literally impossible to achieve in normal gameplay due to how poorly it's coded; it's coded in a way that makes the achievement EXTREMELY easy to void.

From my understanding, the achievement checks if ANY usable OTHER than the survivor melee weapons have been used, and voids the achievement if they were. By "ANY usable [...]" I mean any other usable, this INCLUDES the DEFAULT CLAWS of EVERY SPECIAL INFECTED, alongside THEIR SPECIAL ATTACKS, if they have any.

I CANNOT STATE ENOUGH how A B H O R R E N T L Y bad this achievement is coded. You quite literally CANNOT get this achievement through normal gameplay.

Anyway rant over; this achievement is relatively easily achievable via Rayman's Mutation Mod. To make sure nothing voids the achievement during gameplay we need to do the following: kick all survivor bots, and prevent SI from spawning. Thankfully, Rayman's mod has a Survival mutation that fits the latter criteria perfectly; Hordes.

Launch Hordes on any map, go to the console, kick survivor bots, pick up a melee weapon, making sure to not even fire any weapon or use any items, trigger the waves, and wait for 4/7/10 minutes for a medal to pop up. I've playtested this method on an alt and everything seemed to have worked out well; I got the achievement.

Note, that the achievement specifically states to get a medal, this means you'll have to earn a new medal, whether it's bronze, silver, or gold. If you find yourself in a scenario, where you've already done every map on gold before attempting this achievement, you can download a custom survival map, and start Hordes on it.

Self-explanatory. When playing as a Spitter, wait for either your friend or a smoker bot to constrict a survivor detached from the group, and spit on him. This achievement is quite clunky, so it may take a few seconds for it to be awarded, or rarely it might not be awarded at all. If the latter happens, you'll have to meet the requirements again.

An easy way to do this is to target a survivor that's very low on health, and ride them. After incapacitating them, run away into a safe spot and wait for another survivor to come by and revive the incapped one, which will give you a window to ride another survivor. For an even more reliable strategy, you can do the same as above, but kick the other two survivor bots, leaving just your friend and a bot (assuming you're on the Infected team)

The game needs to be started from the lobby and played until the very end. Very easy to do on a local server with a friend on the opposing team.

The Boomer's vomit is actually a continuous stream of projectiles, which fall in an arc. You can use this to vomit at Survivors either over short walls, or from above, for example whilst on a roof, without being shot.

You simply have to charge a Survivor off an extremely high ledge. The easiest spots do to this in are in the beginning of the first chapter of Dead Center (out of the window), by the end of the fourth chapter in No Mercy (off of the construction site), and the finale in No Mercy (off of the rooftop of the hospital)

It doesn't matter how you hit them, each survivor has to receive at least one tick of damage from the same acid patch. The easiest way to do this is to have a friend group up the bots and themselves into a tight room (i.e. a rescue closet) and have you spit inside.

The chances of me becoming the president of Moldova are higher than that of yours getting this achievement naturally.

If you have a defibrillator, with a friend on the Infected team, try to get a survivor bot killed outside of the saferoom (killing them via friendly fire does not count). For the saferoom flag to trigger, you need to enter the room after the teammate has died. After you entered the room, exit it and go revive your teammate, and the achievement should pop up.

Do note that vertical height also counts towards distance. This means that the easiest way to get this is to probably charge a survivor off the rooftop in the No Mercy finale.

Easiest way to go about this is to host a local Versus server, and have the host kick all other survivor bots. After doing so, make sure the survivor is as close to full health as possible, and charge them. Their high health combined with the scoreboard downtime should hopefully grant you 15 seconds.

The distance needed to travel for a 25 damage pounce is quite long. The best maps for this are the Atrium in Dead Center, and the Memorial Bridge in Cold Stream. The first chapter of Crash Course should also have a spot: from the top of the bridge (the one you'll be crossing after using the howitzer) to the road beneath it. That spot worked in the first game, at least.

Quite easy to do by kicking all other survivor bots and riding the last survivor.

Easier to do than it seems, since the achievement just checks if acid damage hits the survivor after you mount them, meaning you can ride a survivor, and a Spitter can just spit at you (which also means this achievement is unfortunately way easier with 3 human players total)

The easiest SI to do this with would probably be the Charger, due to his mobility. Coordinate with your friend, so that they get into an advantageous spot for you, and charge him.

Most maps should have at least one spot with a very tight hallway/walkway that's required to go through (Dead Center and the Parish come to mind), so this achievement should be possible even in a pub. Otherwise, you can just set up a private lobby with a friend and group up the bots in a tight hallway.

The only way to get this solo, is to follow this guide

With a single friend in the Infected team, this achievement can be earned effortlessly, as after a minute or so, your friend will spawn as a Tank. When they do, no other Tanks will be able to spawn, and additionally your friend will be able to teamkill other Special Infected (and commons), to make the run even easier.

SI will drop presents in Versus around every christmas season, not just the one in 2011, unlike what the achievement suggests.

However, if you want the achievement outside of Christmas, you can set your system clock back to December 15th, 2011, host a singleplayer versus match via the "map [mapname] versus" console command, and farm presents. Do note, that singleplayer versus servers will autokick you after a few minutes due to not having enough players in the server

This achievement is earnable on the first chapter of the Passing in Versus. Coordinating with a friend should be enough to earn this achievement with ease. Note, that impacting a chair too early into the charge might stop the charge.

Overtime occurs when the timer runs out and one of the survivors is holding a gas can. Should be easy to do even in a pub by camping as a Hunter in a safe spot and waiting for the survivor to come to the generator.

Pinning SI like the Hunter, Jockey, Charger, and the Smoker can cause a gas can drop directly, while the Spitter and Boomer will have to incapacitate the survivor in order to do so.

Choose single-round games in the game setup to speed this achievement up a bit.

With enough luck this could be possible even in a pub, that's how I got it at least; lobbies, where you completely roll the opposing team aren't exactly the rarest sight in the world. Make sure to make good use of the Spitter, as a single well-timed acid patch on the generator can erase all of the survivors' progress.

Gas cans with an orange outline can be destroyed by an acid patch. Simply camp in a comfy spot and spew an acid patch every now and then into some unattended gas cans. Note, that you can also earn progress toward this achievement outside of Scavenge, on finales for the Dead Center, the Passing, and the Last Stand.

The game registers a mutation as played either when the player dies, or they escape, winning the mutation, meaning that the fastest way to do this is to launch Dead Center and jump off the nearest balcony.

Note, that you'll have to play a different mutation each time, since the achievement doesn't count the amount of playthroughs, but the amount of unique mutations played. Do also note, that the mutations added with the Last Stand update don't count toward the achievement, so just play official Valve mutations.