I would have to say that the answer to your question is entirely dependent on the individual in question. Emotional abuse and mental abuse are sort of the same thing or overlap. Emotional abuse can be just as damaging as physical abuse. They can both cause devastating long term effects both personally and with relationships involving other people.
I agree that the question is pretty vague and open to various interpretations. I'll go at it from a different angle, I think. The physical, mental, and emotional are all parts of our whole. (I'd also add spiritual, but that wasn't part of your question.) I'm not really a pessimist, but we live in a world which does beat us up on a consistent basis. We're told we need to be smarter, our teeth need to be whiter, how we look isn't good enough...you get the idea. Interestingly enough, then, my conclusion is the same as for abuse--physical is the least damaging, followed by the other two in some sort of a tie. It's one thing to have a bruised body; a bruised heart, mind, or psyche is an entirely more permanent and crushing proposition.
You might want to edit your question, it is a bit vague. Are you asking, among the behavioral aspects which is the most battered in an abusive situation??
I think easily you could argue that the physical "heals" the quickest. It is then a toss up between emotional and mental. Actually, I'd lump the two together and say "psychological" - because in a situation of abuse - I'm not sure that you can separate mental from emotional. Part of what happens in serious abuse is the fact that the mental and emotional aspects of a person are in constant conflict, almost like one tries to take over the other, and vice versa.