It's far easier to do in scavenge then in versus this achievement. Just start a scavenge game with a friend or two and use two controllers on riverbank. Make sure your first controller is the one starting as a infected.
As soon as the game begins have somebody hold a gas can and hide in a corner and have somebody protect him (the AI does a great job protecting the guy with the gas can as well). Now keep spawning and dying with your infected until you can spawn as a charger. As soon as that happens go to the chairs and have a survivor stand in front of the row where most of the chairs haven't been knocked over. Now just hold your RT and charge the survivor through the chairs. Make sure you're not standing too close to the survivor as well.
Good luck this is the TOUGHEST achievement of the DLC because the AI throws such an infinte amount of zombie's and special infected at you while you wait until you finally spawn as a charger. At least while doing this on scavenge you start right away near the wedding instead of having to go over there everytime.
*You can also do this by yourself with two controllers but obviously it's harder. This was confirmed by cradle crue.*
I don't take credit for the video.
I'd like to know what's wrong with this solution that I have 6 negative votes, if you vote negatively I would like to know why. Thanks