His last performance was wonderful; I didn't know he had it in him! [=I didn't know he was capable of such a performance]他最后一场表演很精彩，我过去都不知道他有这本事！

I don't think she has it in her to be cruel. [=I don't think she's capable of being cruel]我认为她残忍不起来。

I don't think she's got it in her to be cruel.我认为她残忍不起来。