Well, if you mean best martial artist it'd be Zell or the monk guy from FFIV. (Forgot his name been awhile ^^)

If you mean overal, fighter, Sephiroth. he has the skill, and ability. But not only that he doesn't give up on anything he sets his mind to.

Plus you have to think about their speed. What of their armor? how much weight are they hauling around. How much do they weigh? And at what jobs do the best exceed in?