Nouns

(n)cheat, cheatinga deception for profit to yourself

Adjectives

(s)adulterous, cheating, two-timingnot faithful to a spouse or lover“adulterous husbands and wives”, “a two-timing boyfriend”
(s)cheating, dirty, foul, unsporting, unsportsmanlikeviolating accepted standards or rules“a dirty fighter”, “used foul means to gain power”, “a nasty unsporting serve”, “fined for unsportsmanlike behavior”