Perhaps easiest done while playing Wingman mode against Easy bots. Make sure to kill one of the two enemies, and if necessary, kill your companion so he doesn't kill the defuser. Plant the bomb and wait for the remaining enemy to start defusing it. Give him a couple of non lethal shots with your weapon of choice, then throw your HE Grenade at him as he's defusing the bomb. As the grenade explodes and kills the defuser, the achievement should unlock!