中山狼 - Chinese Idiom

中山狼:

Literally means:

Zhongshan wolf in the fable - a person who repays good with evil

Actually means:

According to an ancient fable, a wolf was shot in jured in Zhongshan Mountain by a man named Zhao Jianzi, and it went to a gentleman called Dongguo to seek help. The latter put the wolf in his book sack and helped it escape from the hunter. However, the rescued wolf later attempted to take Mr. Dongguo for food.

Later, the term is used figuratively to refer to someone who bites the hand that feeds him or someone who repays good with evil. Derogatory.

古代寓言故事说，赵简子在中山射伤并追杀的向东郭先一只狼，向东郭先生求救，东郭先生把它藏在书袋中，逃过了赵简子的追杀。没想到被救的中山狼后来竟想吃掉东郭先生。

后来一便被用来比喻忘恩负义，把恩人当仇人对待的人。具有贬义色彩。