champion vs proponent

champion and proponent both are nouns.

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

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

Other hypernyms of champion include advocate, advocator, exponent.

champion (noun)	proponent (noun)
someone who fights for a cause	a person who pleads for a cause or propounds an idea
someone who has won first place in a competition
a person who backs a politician or a team etc.
someone who is dazzlingly skilled in any field

champion (adjective)	proponent (adjective)
holding first place in a contest

champion (verb)	proponent (verb)
protect or fight for as a champion