Exar Kun is very close as are Plagueis and Caedus. However Traya's best techniques are all but irrelevant against an opponent this strong. Basically she is demoted to glorified nuisance because of this. Darth Malgus does not have the speed or skill feats to prove to be even as good as Maul.
So in the end this leaves Exar Kun whom is the only one here that might actually prove to be A decent contest.
Darth Sidious wins, Kun isn't good enough to beat him alone.
Originally posted by AncientPower
Sidious has never one-shotted Darth Maul, in all three fights between the two Maul has performed far better than most. Exar Kun may be able to perform similarly well but his team-mates certainly won't.
Sidious one-shot Maul and Savage at the start of the fight. He ragdolled them with them unable to break out despite straining against him. Then as soon as Sidious got bored at the end he started Lokismashing Maul.