They threatened to do him in if he didn't pay the money he owed them.他们威胁他，如果不还钱的话，就干掉他。

He's been so depressed lately that his friends are afraid he might do himself in. [=he might kill himself]他近来非常沮丧，朋友们都担心他会自杀。

He struggled with lung disease for many years, but it was a heart attack that finally did him in.他与肺病抗争了很多年，但最终夺去他生命的却是心脏病。

His inability to attract Southern voters is what finally did him in as a presidential candidate. [=he failed because he was unable to attract Southern voters]他因没能赢得南方选民的支持而在总统竞选中失败。

a businessman who was done in by greed因贪婪而失败的商人

Working in the garden all day really did me in. = After working in the garden all day, I was/felt done in. [=exhausted]在花园干了一整天，累得我够呛。