カイ

く.いる、く.やむ、くや.しい

悔, 忄, 毎, 丿, 毋

心

repent, regret

後悔(こうかい): regret; repentance
悔しい(くやしい): vexing; annoying; frustrating; regrettable; mortifying
悔やむ(くやむ): (1) to mourn; to lament (2) to be sorry; to regret; to repent