Darth Sion vs Darth Malak

Round 1: sabers only no force or regeneration
Round 2: anything goes regeneration allowed

everyone said that revan would beat sion, so i wonder how malak would do

Round 1: Malak wins.
Round 2: If Malak can cut Sion's head in half or do some other move that would at least for a short time stop Sion from using the force, he wins. Otherwise Sion take this.

Malak beats Sion in a lightsaber duel quite easily.

When regeneration is allowed, Sion is well nigh indestructible. Game over.

Malak pwns him in a lightsaber battle.

If Sion his body can't be destroyed then he will win otherwise Malak will take him.