19 Mar 2013 19 Mar 2013
The best place I found to do this is during the first mission of the campaign after the tutorial. Near the end you will begin to fill up a gas can and tons of zombies will begin coming at you. Just wait until there is a large pack in front of you and ensure you have full health.
Walk up to them and within a few seconds you will be grappled, kill the enemy and a second will grab you and so on and so forth. Do this until the achievement unlocks.
There are plenty of other spots to get this but I did it here after a single reload just to get it out of the way early.