Sidious V.S. Nhilus

I think that nhilus would win because he gains power from everyone he kills and stuff so he would ultimately be more powerful.

Nihilus eats him.

nihilus would easily win

Nihilius could conceivably defeat just about anyone - including Revan and Ragnos due to his ability to consume the Force from people. So, he would very well destroy Sidious with ease.

Nihilius is for all intents and pourposes and invincible character unless it is pre healed exile.