champion vs rival

champion and rival both are nouns.

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

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

Other hypernyms of champion include challenger, competition, competitor, contender.

champion (noun)	rival (noun)
someone who fights for a cause	the contestant you hope to defeat
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)	rival (adjective)
holding first place in a contest	as a rival in a competition

champion (verb)	rival (verb)
protect or fight for as a champion	be the rival of, be in competition with
	be equal to in quality or ability