Left 4 Dead 2

I got this achievement legit, but here is a easy way.

a) Start a versus game with 2 controllers on The Parish's first level. (You being the infected)

b) Now, with the 2nd controller, kill 2 other survivors.

c) Now, with your controller, keep jumping into the lake until you become a charger.

d) Put the 2nd controller against a wall, hoping the AI goes near the wall, then charge the AI for 12 seconds. (Charge the AI because most likely in 12 seconds you will have incapaitated the survivor before the 12 seconds)

e) Once it has been 12 seconds you should unlock this!

Well, there is a third way, and it's the way I got it and I've seen this opportunity arise many more times in SCAVENGE mode.

In a SCAVENGE match, people are running everywhere to grab gas cans. A good team will stay together but usually there is always that ONE person that goes off alone.

If you are a Charger, climb up to the second floor right above the race car and go all the way to the left, there are gas cans here and also a door, break it down and wait in there for a survivor. When they one comes by, make your move. There are multiple other similar locations to do this at but you have a great chance at succeeding on upper levels since survivors have to run all the way up there (as opposed to jumping off ledges to save time and rescue each other).

If you're quick with the climbing and good at watching where everyone is going, I'd suggest waiting in the middle (unspawned) and wait until a survivor decides to go off along on an upper floor, then meet them up there! Another plus to Scavenge mode is you have the timer in the upper left corner so you know how long you've been pounding someone's face into the floor for! Good luck!

I've been trying for a while to get this achievement using a two controller versus method without clearing my cache or removing the patch. In the end, I managed it like this:

* Load up versus on the dark carnival, rock concert finale. The gamertag who needs this achievement must be the infected, the other controller can be any survivor but it's recommended you pick your character so you can tell who's who - for the sake of this example, choose Nick.

* Use Nick to quickly kill one of the other survivors.

* Use Nick to open the safehouse door and keep killing the computer controlled infected until your main gamertag is due to spawn as a charger. Defend the safe room, do not leave it.

* Once you're due to spawn as a charger, move to the back of the saferoom, around the corner but don't spawn yet. If you see a message saying 'restricted area', send Nick down the hall and bring him back once the message is gone - usually as far as the restrooms is enough.

* When it's quiet, use Nick to kill the survivor with the least health and heal up the other survivor - for this example, assume Ellis is now the only computer controlled survivor.

* Now, assuming you're not under direct attack, spawn the charger and move the Nick to the back of the safe room so that Ellis follows. Get ready to charge *Ellis* with the charger - you won't get much time

* Use Nick to guard the charger and Ellis from any other attacks whilst the smashing is in progress.

* You should find you get the achievement even if Nick dies after a while as Ellis continues to suffer through the score screens.

Have patience and try again if you don't get it the first time. I'm afraid those 15 seconds seem like a very long time once things are set in motion.