If you don't have a friend to boost with online, this can be done locally with four controllers, too. I had trouble getting to fallen members before the AI did in single play. With the four controllers, kill all the monsters in a room but one. Run players into that monster to die then revive them when he moves on to the next player. You will get the achievement very rapidly. It's much easier with a friend to handle one of those extra controllers but not strictly necessary. Thanks to mfeforever for the tip on leaving just one monster.