sympathizer vs protagonist

sympathizer and protagonist both are nouns.

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

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

sympathizer: someone who shares your feelings or opinions and hopes that you will be successful
protagonist: a person who backs a politician or a team etc.

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

sympathizer (noun)	protagonist (noun)
someone who shares your feelings or opinions and hopes that you will be successful	a person who backs a politician or a team etc.
a person who commiserates with someone who has had misfortune	the principal character in a work of fiction