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