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 

以子之矛,攻子之盾
to turn a person's battery against himself

以柔克刚
Willows are weak yet they bind other wood. (Soft and fair goes far.)

以和为贵
A bad compromise is better than a good lawsuit.

以卵击石
What you do is throw a straw against the wind. (run one's head against a stone wall; Whether the pitcher strikes the stone or the stone strikes the pitcher, it is bad for the pitcher.)  

小Car笔记:

at ease:不拘束,自在,安适
battery:[律]殴打

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