neutralize

verb

1. make politically neutral and thus inoffensive"The treaty neutralized the small republic"
2. make ineffective by counterbalancing the effect of"Her optimism neutralizes his gloom"
3. oppose and mitigate the effects of by contrary actions"This will counteract the foolish actions of my colleagues"
4. get rid of (someone who may be a threat) by killing"The mafia liquidated the informer"
5. make incapable of military action
6. make chemically neutral"She neutralized the solution"