Naga Sadow vs Darth Nyriss

All-out

Sadow

Hard to say, maybe Nyriss

Definetly Sadow

Sadow thru scaling probably takes it. Should be capable of replicating dark side energy blasts like Kun did when he recently wielded it and dueling skills way better than Suriks according to Traya. Also I suppose you can do backwards scaling with his force illusions since his Meditation sphere gave him a 1000x amp to make his fleet and arch 10x larger. Thru this he can make 10 starships and many Massassi/war beasts to help him fight, but I doubt that's possible. At the very least he should be able to replicate Aleemas feats with illusions during battle.

In terms of combat feats, he has nothing aside from stalemating Kressh

but I'm not going to try to convince you Nyriss or Sadow is better