以毒攻毒 to set a thief to catch a thief 以怨报德 He is a person who bites the hand that feeds one. 以逸待劳 To wait at ease till the enemy is exhausted. 以寡敌众 to fight against longer odds 以德报怨 I think it is better for you to render/return good for evil . 以其人之道还治其人之身 to pay somebody (back) in his own coin