neutralize vs countervail

neutralize and countervail both are verbs.

Word	Noun	Adjective	Verb	Adverb
neutralize	No	No	Yes	No
countervail	No	No	Yes	No

As verbs, neutralize and countervail are synonyms defined as:

neutralize and countervail: oppose and mitigate the effects of by contrary actions

Other synonyms of neutralize include counteract, counterbalance.

neutralize (verb)	countervail (verb)
make chemically neutral	oppose and mitigate the effects of by contrary actions
make ineffective by counterbalancing the effect of	compensate for or counterbalance
make incapable of military action
get rid of (someone who may be a threat) by killing
make politically neutral and thus inoffensive
oppose and mitigate the effects of by contrary actions