resister vs opposer

resister and opposer both are nouns.

Word	Noun	Adjective	Verb	Adverb
resister	Yes	No	No	No
opposer	Yes	No	No	No

As nouns, resister and opposer are synonyms defined as:

Other synonyms of resister include adversary, antagonist, opponent.

resister (noun)	opposer (noun)
someone who systematically obstructs some action that others want to take	someone who offers opposition
someone who offers opposition