You're a horrid, mean thing.

你这个令人讨厌的自私鬼。

Certainly not! I won't do such a mean thing.

当然不是！我才不会做如此卑鄙的事。

Cheating such an old man was a mean thing to do.

欺骗这样一个老人实在很卑鄙。

The mean thing! I told her not to tell you I told her.

卑鄙的东西！我叫她不要把我跟她说的告诉你。

He asserted again that he didn't do such mean thing, but nobody believed.

他一再声称自己没有做那么卑鄙的事，但没人相信。