噯 [嗳] ài : (interj. of regret)

Big5: , Unicode: 566f (噯),
Links: MT, Cantonese, Ld, Chinese Language

懊 ào : to regret

Big5: , Unicode: 61ca (懊),
Links: MT, Cantonese, Ld, Chinese Language

懊 悔 ào huǐ : feel remorse; repent; regret

抱 恨 bào hèn : have a gnawing regret

抱 歉 bào qiàn : be sorry; feel apologetic; regret

懺 [忏] «懴» chàn : feel remorse; regret; repent

Big5: , Unicode: 61fa (懺),
Links: MT, Cantonese, Ld, Chinese Language

悵 [怅] chàng : regretful; upset; despair; depressed

Big5: , Unicode: 60b5 (悵),
Links: MT, Cantonese, Ld, Chinese Language

感 慨 gǎn kǎi : lament; with a tinge of emotion or regret

嗐 hài : exclamation of regret

Big5: , Unicode: 55d0 (嗐),
Links: MT, Cantonese, Ld, Chinese Language

憾 hàn : regret

Big5: , Unicode: 61be (憾),
Links: MT, Cantonese, Ld, Chinese Language

很 遺 憾 hěn yí hàn : unfortunately; regrettably

後 悔 hòu huǐ : regret; repent

回 歸 huí guī : to return (to previous condition); Hong Kong's return to Chinese sovereignty; to regress

悔 huǐ : regret

Big5: , Unicode: 6094 (悔),
Links: MT, Cantonese, Ld, Chinese Language

歉 «欠» qiàn : apologize; deficient; to regret

Big5: , Unicode: 6b49 (歉),
Links: MT, Cantonese, Ld, Chinese Language

退 步 tuì bù : degenerate; regress

遺 憾 yí hàn : regret; pity; sorry