winner vs contestee

winner and contestee both are nouns.

Word	Noun	Adjective	Verb	Adverb
winner	Yes	No	No	No
contestee	Yes	No	No	No

As nouns, contestee is a hyponym of winner; that is, contestee is a word with a more specific, narrower meaning than winner:

winner: the contestant who wins the contest
contestee: a winner (of a race or an election etc.) whose victory is contested

Other hyponyms of winner include medalist, medallist, upsetter, walloper.

winner (noun)	contestee (noun)
the contestant who wins the contest	a winner (of a race or an election etc.) whose victory is contested
a gambler who wins a bet
a person with a record of successes