遺恨[ikon] grudge
怨恨[enkon] enmity
悔恨[kaikon] regret
逆恨み[sakaurami] being resented in return
旧恨[kyuukon] old grudge

恨み[urami] resentment
恨みっこ無し[uramikkonashi] with no hard feelings
恨みっこのないように[uramikkononaiyouni] making it even
恨み言[uramigoto] grudge
恨む[uramu] to resent

悔い[kui] regret
悔いる[kuiru] to regret
悔改める[kuiaratameru] to repent
悔しさ[kuyashisa] chagrin
悔泣[kuyashinaki] crying from vexation

悔み状[kuyamijou] letter of condolence
悔む[kuyamu] to mourn
悔悟[kaigo] remorse
悔恨[kaikon] regret
後悔[koukai] regret