rat piece of shit

A person who comes across as a nice guy, but is really a two-faced asshole.

Q: Is it nerve-wracking for you to do something like this? Or is it more nervous for you to box?

A: It's more nerve-wracking to be here talking to a rat piece of shit like you.

Phrase coined by former heavyweight champion Mike Tyson, in a Toronto television interview on Sept.10/14