Master Anhan

I agree. Also in KotOR II it is mentioned on Korriban that the true master duelists lived long before the time of even the Exile and Revan. So in terms of pure duelling ability regardless of style, the ancient Sith Lords were the best. Even though technically the Sith Lords were a body of people and not a singular person. (I can't think of a name off the top of my head)