Chinese equivalent of "a bad apple spoils the barrel" What is the Chinese equivalent of the English idiom "a bad apple spoils the barrel"?
Chinese has an idiom: 害群之马, it refers to the bad apple which spoils the barrel. Literally, it says : a horse that brings trouble to its herd.

“a bad apple spoils the barrel” also has a Chinese counterpart: 一个老鼠屎坏了一锅汤, but it is kinds of rude, maybe.