This trophy has a very small hint of luck about it. But it is actually pretty easy to get. When you get a berserker to low health, it will run at you in a craze and try to blow itself up in close proximity to you.
The best way to go about getting this is to let a few of the regular small creepers mull around you in an area where there is a berserker. Start laying waste to the berserker and when he is low enough health, let him charge you. If you have a few small creepers around you when he blows up, he should take them with him. Trophy is yours!