I think Vader and Kun have the best chances here based on their specializations. Defensive/tank capabilities and unpredictability are two of the most important things in a fight like this. Kun's style is the most unpredictable, and Vader's has the best defense paired with his armor. I'd say Vader is the second most unpredictable fighter while Kun is probably the weakest tank here, so I'd give this one to Vader.
Originally posted by Q99
What's he got for defense above the norm? Offense, he has amulet blasts...
Force Barriers powerful enough to only be defeated by a Sith spirit in Freedon Nadd and an Ancient Jedi Master with a millennium of prep for such an occasion.
Shown the ability to successfully defend against Sith Sorcery such as Keto's and is immune to Force Drain.
He also has the ability to freeze lightsabers on the spot. A black variant of lightning that surpassed lightsaber conduction and an offensive Essence Transfer technique(which is strikingly similar to Dark Transfer).