Darth Nox easily, IMO.
Darth Nox specializes in esoteric matters of the Force as well. He not just acquired the capability to summon deadly tendrils like Zannah but mastered the Force-walking talent to such a degree that he was able to summon the power of 5 additional dark side warriors (besides his own) during a battle to utterly destroy a canonically "supremely powerful" opponent.
I don't see how anybody can match Nox unless he is prime Luke, Sith Emperor, The Father and/or Sidious.
Originally posted by Lord Stark
Well if this is Talzin with prep she dominates excellentWithout prep this is an interesting battle. Talzin has the chops to fend off Master Windu for sometime as well as surround herself in a barrier and blast Darth Nox with lightning.
1. Himself
2. Darth Zash
3. Lord Ergast
4. Darth Andru
5. Kalatosh Zavros
6. Horak-mul
In addition, Nox can tank extremely potent Force powers without any issue. I seriously doubt that Talzin can even hurt Nox. On top of this, Nox's immense Force powers would be more then enough to destroy Talzin.