na-adjective, noun
hates losing; competitive; sore loser
Describes a person who strongly dislikes losing and will go to great lengths to win or avoid admitting defeat. Can be used positively (determined, competitive) or negatively (stubborn, ungracious).
彼は負けず嫌いだから、どんなゲームでも本気で勝ちにいく。
He hates losing, so he seriously tries to win any game.
Her competitive nature helped her grow.