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Ludo Kressh and Nomi Sunrider at their best against ROTS Mace Windu.

Well Nomi's a beast with the saber and is immune to Vaapad's anti-darkside effects but she would still lose to Mace. I don't know who Kressh really is or how good he is but I seem to recall him standing up to either Nadd of Ragnos which puts him pretty high. I don't know about saber. could go either way.
But mace gets his ass handed to him in a force fight. Kressh is probably his equal and Nomi would whoop him either with BM or with Force separation.
If it's all out the Mace losses.

Ludo stood up to Naga Sadow, Ragnos is dead by then and Nadd doesn't live for another 400 years.

Damn!! I really need to read those books.
How's Sadow then? Any good for a comparison?

Well, he was Dark Lord of the Sith after Marka Ragnos, but we didn't really see much in the way of dueling from him.

Naga Sadow was one of the most accomplished Sith alchemists in the mythos.