opponent vs doer

opponent and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
opponent	Yes	Yes	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of opponent; that is, doer is a word with a broader meaning than opponent:

Other hypernyms of opponent include actor, worker.

opponent (noun)	doer (noun)
someone who offers opposition	a person who acts and gets things done
a contestant that you are matched against

opponent (adjective)	doer (adjective)
characterized by active hostility