Nearly all words that end in <oon> have the main stress on the final syllable. Examples:
afternoon baboon balloon bassoon buffoon Cameroon dragoon harpoon lampoon macaroon monsoon saloon tycoon typhoon Walloon
Words ending in <zoon> are different. This ending is pronounced ˈzəʊɒn or ˈzəʊən. Example: ˌprəʊtəʊˈzəʊɒn.