Left 4 Dead

I got this on the Farmhouse finale. At the start of the level. Near the trains. He came out from a tree. I used auto-shotty at his head running backwards while the others were shooting at him too. I know hes very random. But, if you don't see a witch its guaranteed you'll see a tank.

Make sure you have tons of room to run around. His reach is pretty huge.

a good spot that will sometime spawn a tank is next to the elevator shaft before reaching the roof of the Mercy Hospital. If you start to crawl through the small grate to enter the shaft, a special infected will spawn. if it turns out to be a tank, just crawl backwards (make sure you press crouch first or you wont automatically start crawling backwards). Then have everyone fire through the little window at it until hes dead. also if you have any molotovs left you can toss it in there and let him burn (while getting the cheevo for that too).

This can be done extremely easily on the No Mercy Finale

Once the tank comes there is a way to get him stuck so you can kill him easily. Stand right above the ladder to the left of the Mounted Gun. Stand as far over the edge as you can without falling off.

Now, if the Tank comes from the left than he will see you and try to climb the ladder to get to you. DON'T MOVE and he will try to climb the ladder and get stuck. From here you can kill him however you like, but the shotgun would be most efficient as you will be right next to him.

The only problem you may have is the tank throwing a rock at you. If you notice him throwing a rock you'll either have to shoot it so it wont hit you, or run away and dodge it. Either way you'll need to get back there before the tank gets to the ladder.

However if the tank comes from the right side this wont work, and you'll have to wait for another tank to use this method, but keep trying, eventually a tank will come from the left.

EDIT: Found a video of what I meant. This is done on a PC and the player spawned the tank, but it works the same on the 360

EDIT: He also did this on expert difficulty, if you do it on easy it will take considerably less shots to kill.

It's possible to do this on BH finale with 3 bots. If you stay out in the open, it's easy to tell where the tank is coming from and you can start shooting him from far away. The most important aspect of this is the rocks that the tank throws. It's possible to shoot the rocks out of the air, but it's better just to dodge them.

We actually got this one at the Boat House Finale - there should be several Molotovs there. Grab one, wait for the tank music, and toss the first one when he starts shambling in. If you catch him on fire, you're halfway there. Toss another molotov when it starts to burn down. And have at least one person focusing the mini gun on the tank.

i got it with an auto shotgun on single player normal campaign, nobody was helping at all, its really easy actually, you gotta be a bit more possitive about it

I got this achievement playing on Dead Air finally. It is probably easier with others but still possible with bots. when the tank spawns you want to make your way to the escape vehicle (plane) and ensure you are on the opposite side to where the tank is.

Now you can run around the plane shooting at him but quite often he actually gets stuck on the plane. Once he does all you have to do is crouch and shoot him under the plane. This goes without saying but this is best done on an easier difficulty as it takes less to kill the tank.