✔ 最佳答案
Black sheep (n) [C usually singular]
Someone who is regarded by other members of their family or group as a failure or embarrassment
From Longman Dictionary of Contemporary English
Person regarded as a disgrace or a failure by other members of his family or group 害群之馬,敗類
From 牛津高階
參考: 牛津高階 and Longman Dictionary of Contemporary English