My vote would go to Nihilus. Sion would be difficult to defeat bc he would be better in terms of lightsaber skills, but Nihilus would just use extremely powerful force powers to keep him at bay taking away Sion's advantage

Nihilus!!! Sion ain't got a chance! If u some how got rid of Nihilus' force powers mabe Sion then, Nihilus rules all!!!

 

I love Nihilus he rocks!!!!

 

 

Chewy knows all!! lol!!!

Well sure, Sion is no match for Nihilus, but I prefer sleeps-with-vibroblades. Nihilus was foolish to take the path he did, suicidal, maybe he figured it was worth early death, to hold power of that magnitude, the ultimate power in the galaxy