Synonyms for Neutralize (same or very similar meaning)
WordNet sense 1 (oppose and mitigate the effects of by contrary actions):
counteract, counterbalance, countervailWordNet sense 2 (get rid of (someone who may be a threat) by killing):
liquidate, waste, neutralise, knock off, do inWordNet sense 3 (make ineffective by counterbalancing the effect of):
negate, nullifyFrom the ODE community, based on WordNetadd/edit