self-willed; doing things to suit one's own convenience
Describes a person who acts or speaks in a way that prioritizes their own convenience or desires, often without regard for others. Commonly used as a な-adjective or noun.
I can't stand his self-willed attitude anymore.
If you act only to suit your own convenience, you'll lose the trust of those around you.
A yojijukugo combining 得手 (one's strong point, what one is good at) and 勝手 (one's own convenience, selfishness). The exact historical derivation is uncertain, but the compound conveys the idea of doing things in a way that suits oneself.