doubter vs doer

doubter and doer both are nouns.

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

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

Other hypernyms of doubter include actor, worker.

doubter (noun)	doer (noun)
someone who habitually doubts accepted beliefs	a person who acts and gets things done
someone who is doubtful or noncommittal about something