As One Pleases
One's Own Convenience, One's Own Way, One's Way
noun, な adjective
The hand (or person, as you know 手 often refers to a person) that wins gets to do as one pleases without regard for anyone else.
The reading for this is weird. It's all kun'yomi, which luckily you've seen before, but still strange. I guess when you do as one pleases you can read kanji however you want, in this case the kun'yomi readings. Do note that there's a small っ in there before 手, presumably to connect the two readings of the two kanji together.
身勝手
selfishness
好き勝手
doing what one pleases
自分勝手
selfishness
勝手にやる
to do as one pleases
勝手にする
to do as one pleases
勝手にしまう
to put away without permission
勝手な思いこみ
a groundless assumption
勝手な人
a selfish person
勝手な事
something done without due consideration
ほんと、勝手だよね！
You are so selfish!
勝手なことばっかり言わないでよ！
Don't say whatever you want.
「サーモン！フグは五回も浮気したんだよ。そんな男のこと、信じちゃダメだってば。」「分かってるんだけど、でも、彼、私がいないと生きていけないって言うの。」「じゃあ、もう、勝手にすれば！」
"Salmon! Fugu cheated on you five times. Never trust a guy like that." "I know… but he says he can’t live without me." "Well, suit yourself then!"