protagonist vs proponent

protagonist and proponent both are nouns.

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

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

Other hypernyms of protagonist include advocate, advocator, exponent.

protagonist (noun)	proponent (noun)
a person who backs a politician or a team etc.	a person who pleads for a cause or propounds an idea
the principal character in a work of fiction