[@Savato]
Personally I put her somewhere around Mach 50, but I only have limited knowledge on Naruto.

[@dirty slime]
All Sidious has is a statement that he's the most powerful. But Vitiate, by feats, annihilates him.

Sidious drained a planet over an extended period of time. Sidious instantly life-wiped an entire planet, including dozens of Jedi Masters and incredibly powerful Sith. He mind-controlled an entire planet's population at once, and unlike with Sidious, he does it instantly, and then makes the planet's population start killing one another. And he also mind controlled 8000 Sith at once, and performed another planet-wide lifewiping attack, although that one was a ritual. Vitiate's lightning was so powerful that Revan, a master of Tutanamis capable of absorbing lightsabers and lightning from elite Sith, was burned to a crisp just trying to absorb it. Vitiate was able to bare-handedly casually swat away the lightsaber of one of the most powerful Jedi in the galaxy, and broke the minds of Jedi masters with nothing more than a glance.

Sidious ain't got shit on Vitiate.