spoiled sport
Petty, spiteful complaining after losing a sporting event.
The spoiled sports pummeled our mascot after we won the big game.
spoil sport
A person who ruins the fun or the enthusiasm of others.
"Come on, let's go to your cousin's party tonight and have some fun!"
"No, it won't be fun, and my cousin is NOT cute"
"Aw, don't be such a spoil sport!"
"No, it won't be fun, and my cousin is NOT cute"
"Aw, don't be such a spoil sport!"