I'm not 100% sure, but I think that to get this achievement you must kill 3 or more enemies by rolling the Bowling Bomb. So find three or more enemies, take some distance (you must not hit them directly with bomb), throw the bomb and cross your fingers. Tight places with a lot of enemies are the best to try this achievement, just remember to kill the enemies by rolling the bomb: if you find a good spot, quicksave and quickload your game until you have got this achievement. You can see this achievement's progression by looking at your Ion Fury's Steam achievement section (but they aren't updated in real time).