What is the exact word for someone who always pretends to be nice to someone's face but makes fun of them behind their back?

Even when he/she is talking to you he/she will treat you very good like a good-mannered person. 

He/she very much cares about his/her image in front of everyone like a celebrity wants to show a positive image of himself/herself in front of audience. But they are not actually good from heart.

*Any word except* ***hypocrite***.