retaliate by similar behaviour
以其人之道，还治其人之身
said ironically when introducing a banal remark or cliché
套用一种说法
I had to find out the hard way—to coin a phrase.
套句老话说，我是费了九牛二虎之力才搞清楚的。
One of two differing or opposing views or sides.
反面，反面意见：两个不同的或相反的观点和方面之一