Canon I would have to choose Yoda, he was the only one who ever came close to defeating the emperor in a straight fight (Don't know about the clones, I haven't read those books, but I'm thinking that if he was anything like the Clone Troopers and Jorus C'baoth, he wouldn't have the same experience or memory's as the original.)
Non-Canon I choose Kyle Katarn. He killed Jerec, defeated Tavion, and killed Dessan, not to mention Jerecs minions and Desanns hordes of reborn and shadow warriors. That totals to about 50-200 (I didnt count) reborn/shadow warriors, 2 and a half Sith Lords (Tavion wasn't a full sith) and atleast 7 trained Dark Jedi. That's one helluva resume.
Edit: By Canon/non-canon, I mean the movies and everything else, respectively.