害人反害己 [- - fǎn hài jǐ]be hoist with [by] one's own petard; Cruses (like chickens) come home roost; Harm set, harm get.; Harm watch, harm catch.; recoil on [upon] oneself; The biter (is) bit [bitten].：
•¶ 设圈套陷害他的对手固然是个妙计， 可是到头来却是害人反害己。 It was indeed a clever plan to entrap his opponent， but in the end he was hoist by his own petard.