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

懐旧[kaikyuu] recalling the old days
旧ソ連[kyuusoren] former Soviet Union
旧悪[kyuuaku] past misdeeds
旧衣[kyuui] worn-out clothes
旧詠[kyuuei] ancient poems

旧怨[kyuuen] old grudge
旧縁[kyuuen] old relationship
旧恩[kyuuon] old favors
旧仮名遣[kyuukanazukai] former (i.e. before the post-WWII reforms) kana usage in writing the readings of kanji