Although Sora is good, I have to go with Ventress on this one. There is a reason Dooku made her commander. Bulq was brought over and convinced to turn on the Jedi by Dooku, he was never really filled with the darkside.... while Ventress was teeming with the Darkside, before Dooku even came into the picture.
Sora. They both fought Mace Windu in The Defense of Kamino. Sora fought bravely but I think Mace Force pushed him into a pile of rocks and they landed on him.He survived. Then he and Asajj fought. Asajj got scared of Mace's power and fled like a coward. On the other hand didn't Quinlin Vos kill Sora? Ah well, I'll say Sora.