So, to bump.
Points for Vader (no order):
- He still has potential rivaling Sidious (double before, cut in half)
- He has cybernetics and a lightsaber resistant suit
- His feats and accolades as a duelist seem to be superior; Kun was a prodigy, but Anakin was a GOAT contender, and Vader retained that skill
- He almost certainly has more raw power with respect to Force augmentation
- His TK feats are incredible
- He does have experience with sorcery
Points for Kun:
- He shattered lots of beskar casually (this might actually be the most impressive lol)
- He beat JA Luke while a weakened spirit, albeit with Kyp's help
- He may or may not have TK'd a capital ship
- He did a TP thing to a city-planet, allegedly to every technician in it, but some would say just to those in the surrounding area
- He was a prodigious swordsman having invented his own form, and has the agility and mobility advantage over Vader
- There are some quotes putting him above previous ancient sith and whatnot
- He has lots of potent sorcery abilities
- He has an unorthodox form (so does Vader, but likely to a lesser extent)
I'd side with Exar if I take more generous interpretations of the beskar shattering, beating Luke, and his TP/TK feats. I'd side with Vader if I take more moderate stances.
Vader's probably the better swordsman; Exar inventing that form isn't as impressive by Vader's time given the proliferation of double-bladed sabers, whereas Vader's former destruction of masters like Dooku impresses me more, especially given his likely advantage in augmentation. This could all change depending on the beskar thing.
In the Force...well, you could say that Luke was blindsided and didn't know about that sorcery, whereas Vader does to some extent. Plus Vader would be able to retaliate whereas Luke in that context really couldn't. Vader's TK might actually give him the win; it depends on that really weird starship feat that might not even be a feat at all.
Overall, I'm leaning towards Vader; he has enough knowledge of sorcery to counter, and the beskar shattering might not be as impressive as we don't know how shatter resistant it is.