Darth Bane, quite easily. Technically, he's an outright prodigy, learning every move and sequence to the saber staff as well as becoming the best duelist in the most martial order of sith thus far seen, all under two years of training. That being said, he can wield said double-bladed saber with mastery of all 7 forms, Kas'im's advanced ones that is. Speedwise, at only a fraction of the power he gains in Bane of the Sith (as in before going through 4 major power surges, gaining a further year's worth of experience, as well as the benefits gained from the orbalisk armour) he was able to move at speeds completely invisible to the eyes of trained force users, including Kas'im who was noted for his incredible reflexes. Strengthwise, he's a beast of a man, virtually 7 foot tall, and described as a 'mountain of muscle,' with an incredible command of the force to enhance his strength with. His command over the force is ridiculously strong, to the point where he can control and direct enough power to wipe out an entire planet, and play around with moons as if they were pingpong balls. He quite simply has anyone beat, with the force or saber combat.