I have completed game in 4 hours and obtained all achivements. This guide might not be completed but it's made to help people who are playing for the first time. If you have any feedback or if you see any completed achievement that you would like to add something to, let me know in the comments! Thank you in advance.

Obtain your first skill chip

At beggining of tutorial you will be required to go deeper down in subway station behind last door (2nd) there will be your first skill chip located on table. Simply take it by pressing " F " and achivement will pop up.

Kill 10,000 zombies.

This achivements will come naturally and it's not much of grind, you don't need to kill 10.000 zombies in single run, it can be done trough multiple walktroughts. Fastest method is to play endless mode and clear floor after floor, leaving no one behind by reaching station 20 without dying and following this method, should gather enought kills for achivement to pop up.

This applies to achivement stated bellow which can be stacked:
" The first step ", " Zombie Blender " , " Zombie Slayer " and " Nightmare of the Undead ".

Kill 1,000 zombies.

Kill 100 zombies.

Kill 10 zombies

kill 1 zombie

Obtain your first legendary weapon.

Legendary weapons are spawning randomly in subway stations and they can be easly spotted as they are glowing yellow. Once you find one simlpy take it by pressing " F " and achivement will pop up.

Get 100 legendary weapons.

As stated above, legendary weapons spawns randomly in subway stations. This achivements will come naturally, it can be done trought multiple walktroughts. Fastest method is to play endless mode.

SIDE NOTE: There is also legendary weapon at end of game inside train at City Hall station and once you completed campaign legendary can be found at early beggining of game when entering train for first time near train's main console.

City Hall last station:

New game - Early Beggining 1st station.

Check out the credits.

While in main menu section press " credits " and achivement will pop up.

Hidden achivement

Clear the campaign mode by completing all 9 subway stations or to be exact by reaching City hall station.

NOTE: There is no zombies at city hall station.

Max out all skills.

To max out all skills you need to collect skill chips but this can be easly done in endless mode if you search subways thoroughly. It's possible to get up to 10 chips in single train station and once reached 9th you should have enought skill chips to upgrade everything to max.

NOTE: To upgrade skills with skill chips press "tab", it can be done in any time but game won't be paused so be aware of zombies. Additionaly to this they will be randomly placed inside train stations.

SIDE NOTE: When you max out all skills, you can still find and spent chip skills on hp or base damage which incerase: +5 HP per chip skill or +1% base damage.

Clear Stage 5 in Endless Mode.

NOTE: If you are playing steam in offline mode you won't be able to obtain achivement !
Don't ask how I Know.

Reffer to achivement : " Aiming for the Top ".

Clear Stage 10 in Endless Mode.

Clear Stage 20 in Endless Mode.

It's aren't hard as it seems, you have enought time, focus on gatherin skill chips so once you max out all your skills, I would recommend to go for HP. Each skill gives +5hp additinaly or +1% base damage. Tatic which I used to reach stage 20 is simply collecting either legendary (Yellow) or epic (purple) weapons and not rushing inside but going slowly and cleaning floor by floor until I get all chipset skills even in later stages I use same tactis for gathering fuses and than rush back in train and here is simple trick how to pass it quickly. Follow green lights it's pathway to staircases once you reach them always hold right or left side of closer to wall if there is no incoming zombies on top you can jump from top of stair to get very quick at bottom while doing so be sure to have weapon which can make explosion radius to clear zombies before landing or any weapon which can 1 hit zombies and penetrate true them such as sniper (purple) or any legendary weapon basically. When it comes to upgrade for begging it's priority to spend on Health to have at least 190 (3 chips) after recovering 2hp per kill (3 chips) and More ammo for weapons.

Clear the Campaign Mode within 20 minutes

It's aren't hard as it seems but it's tricky. Time to learn speedrunning. I strongly recommend to play and complete at least 20 Stages of endless mode before even attempting this one to learn game mechanic better and to learn how to obtain fuses faster. Your First focus will be time, it's everything meacning there is no time to waste even for chip skillsets, strictly collect fueses eventually chips if they are in same room and bunnyhop, bunnyhop, bunnyhop. When it comes to upgrade for it's priority to spend on Health to have at least 190 (3 chips) than recovering 2hp per kill (3 chips) and More ammo for weapons 100% (5 chips).

Tatic is simple, get out of train and imidiatelly start running to upper floor, collect either legendary (Yellow) or epic (purple) weapons than rush inside every room by checking wall if there is yellow jump past zombies and collect it when coming back to door simply kill zombies as they will be stacked, best is to use any legendary weapon or weapons with explosive blasts. Don't waste time on collecting skill chips. First 6 subway stations must be completed fast as there is 1-3 fuses in total. Sometimes you are lucky to find 3 fuses on First floor in just 2 rooms it all depends on luck and how fast you are but for best result focus on this timings:

1st / 2nd Subway Station = 1 Fuse - 45 sec = 1.5 min
3rd / 4th Subway station = 2 Fuse - 1 min 15s = 2.5 min
5th / 6th Subway station = 3 Fuse - 2 min = 4 min
7th / 8th subway station = 4 Fuse - 3 min = 6 min
9th Subway station = 5 fuse - 4 min = 4 min

This quick "speedrun - station walktrought" should help you improve your timing:
Link: https://streamable.com/jjhclt

The key is to rush back in train and not losing time for killing incoming zombies so here is simple trick how to pass it quickly. Follow green lights it's pathway to staircases once you reach them always hold right or left side closer to wall if there is no incoming zombies on top you can jump from top of stair to get very quick at bottom while doing so be sure to have weapon which can make explosion radius to clear zombies before landing or any weapon which can 1 hit zombies and penetrate true them such as sniper (purple) or any legendary weapon basically. Than keep jumping to the Train. Once there imidiatelly hit HP regeneration and hit train to arrive fast in that 4 seconds use tab for upgrades and start bhop as soon as doors open.

Thank you for visiting, please leave your feedback in the comments and rate the guide if this has helped you in any way.