game-change

or game change

[ geym-cheynj ]
/ ˈgeɪmˌtʃeɪndʒ /

noun

a dramatic change in course, strategy, basic character, etc.: Her feelings for him have undergone a game-change.
game-changer: He was a game-change, and an asset to the company.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019