Left 4 Dead

I Made this Tutorial Video for this and the Back 2 Help achievement

Easily gotten in split-screen with another controller. Make sure your guest is a survivor with 3 bots. Using the guest, lower their health enough so that one shotgun blast will down them. I'd recommend using the auto shotgun and try and get them to space out so they aren't picking each other up.

Play splitscreen Versus on Crash Course with yourself/lil sister/friend. The gamer who is getting this achievement (GamerA) should be the special infected, while the other, survivor (GamerB)! At the end of the last level, after turning the generator on (once). If (twice) then the bots would be heading towards the Armor Truck when the door opens, leaving you.

Steps:
1.(GamerB). All survivors must go to the back were you entered the junkyard, make sure the survivors, at least 3, are next to a car.
2.(GamerA) When you turn into the Tank, sneek around making sure that the bots don't see you, that's what (GamerB) is for, he guids the sheep lol
3.(GamerA) Approach the opposite of the car, were (GamerB) and the bots are, as the Tank, and hit, SLAM!

Achievement appeared for me by accident lmao (I was trying to get "20 car pile-up") but was more suprising was that I hit all 4 survivors and gained 2 achievements! Wipefest(35) and All 4 Dead (30) BOOYA! So if you don't have All 4 Dead, this is how (easy) :]

Comment if you want gameplay help :]

I got this achievement by incapping 3 survivors with a guest account, just lower each survivors health enough so that one shotgun shot will incap them, and the achievement should unlock.
This is an achievement that is bugged so you must be offline versus.

this one is not as bad as it sounds (if you want to boost it that is) go to splitscreen and go to the finale. make yourself the infected. let the survivers have their fun untill the truck is open. have your guest stand right in front of the truck. the cpu players will go into the truck and just sit there. have your guest shoot into the truck untill they are all low health. (dont worry about downing one, the computers will heal him) when they are all in low health pick up your controller. now since this is the last part of the finale you will be the tank. just run into the truck and hit twice. and then you will have it. ( and if you want you can kill your guest for another achievement)

Bizarrely you don't have to be infected. I got this by accident trying to get the bots out of the way for another achievement.

Start up versus with yourself as a survivor and guest as an infected.
Keeep hitting A until you get a local server as all the achievements are glitchy on dedicated servers. Shoot all the bots til they have low enough health that a shotgun will take them out and then shoot them all one more time each.

Bingo. Achievement!

I do not take any credit for this video, all credit goes to KatamariHero for making it. A lot of people thought that this had to be done within five seconds of the campaign starting, it is incapacitating three survivors within five seconds. Hopefully when you guys attempt this you will do it as easy as the guy in the video, and your bots will not wander off and teleport.

In a Versus match, using 2 control.
The control that you want to get the achievement must be the infected and the other one survivor.
Don't spam, only pick up the survivor control and shoot in the 3 boots (You don't need to get out in the safe house).
When all 3 bots get the red life, reload and kill the 3.
POP.
Ps.: If this not work, the problem is the server (This valve server is sooooo problematic).