endorser vs protagonist

endorser and protagonist both are nouns.

Word	Noun	Adjective	Verb	Adverb
endorser	Yes	No	No	No
protagonist	Yes	No	No	No

As nouns, protagonist is a hypernym of endorser; that is, protagonist is a word with a broader meaning than endorser:

Other hypernyms of endorser include admirer, booster, champion, friend, supporter.

endorser (noun)	protagonist (noun)
someone who expresses strong approval	a person who backs a politician or a team etc.
a person who transfers his ownership interest in something by signing a check or negotiable security	the principal character in a work of fiction