noun
hard-to-please person; grouch; sourpuss
Describes a person who is habitually difficult to please, picky, or grumpy. Often used in a mildly critical or humorous way.
See also: 気難しい
うちの祖父は気難し屋で、何をしても文句を言う。
My grandfather is a hard-to-please person; he complains no matter what you do.
あの気難し屋の上司を満足させるのは大変だ。
It's tough to satisfy that grouchy boss.