Similar word to annihilate:

abate, abolish, abrogate, annul, blot out, crush, decimate, demolish, do in, eradicate, erase, expunge, exterminate, extinguish, extirpate, finish off, invalidate, liquidate, massacre, murder, negate, nullify, obliterate, quash, quell, raze, root out, rub out, ruin, slaughter