The Achievements that we'll aim to unlock are:
ALL 4 DEAD: Incapacitate or kill all four Survivors in one life as a Tank



WIPEFEST: Your team incapacitates three Survivors within five seconds in the Crash Course campaign.



20 CAR PILE-UP: As a Tank, hit 20 Survivors with a car in the Crash Course campaign



DEAD WRECKENING: Dole out 5000 total Survivor damage as a Special Infected



The first two achievements are difficult to get, especially if you're against experienced players or/and random teammates.
The third achievement is tedious since it requires some basic dedication and skills to the Versus game mode
The fourth one is easy to get by playing normally, but if you have no patience at all you can get it my way.

Before Starting you should enable the command console by navigating:
Options->Keyboard/Mouse-> ALLOW DEVELOPER CONSOLE


Disclaimer: The guide involves enabling the in-game cheats in order to get the achievements solo

Step 1: Open console and insert the command "map l4d_garage02_lots versus"
The game will load the second half of the crash course campaign in versus mode.
If you automatically join the survivors exit and load the level once again
If not you are good to go

Step 2: Move close to the car and aim at it as depicted in the following photo.

Step 3: Insert the commands in this order.
It's a HARD requirement to write them in between the sv_cheats commands so as to fool the game to allow achievements to be obtained. Otherwise it won't work.
The former command teleports all survivors to the location that your crosshair targets. So by looking at the car the survivors will be stuck at it and not move, up until they attack any infected.
That's why you should immediately enter the latter command.
This one spawns a tank in the map, which you'll automatically take control of, since you're the only player in the lobby.
After that you should hit the car and all survivors will be incapacitated, as depicted in the video.

By incapacitating 4 survivors at once will reward you both the ''All 4 Dead'' and the "Wipefest" Achievements.
If you repeat the process 5 times you'll be granted with the "20 CAR PILE-UP" achievement
Repeating this method enough times will grant you the "DEAD WRECKENING" achievement aswell.
Credits:
The "enable-disable cheats" exploit has been known forever in Valve's old videogames, and the console commands are available in Left 4 Dead Wiki and almost everywhere. I collected and sorted all that ubiquitous information.