champion vs competitor

champion and competitor both are nouns.

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

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

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

champion (noun)	competitor (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)	competitor (adjective)
holding first place in a contest

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