Not only would Sidious beat the massively Pre-Prime incarnation of Darth Revan, he'd beat him in his prime as a Jedi. Revan is inferior to Yoda, who up until his time was the most powerful Jedi (and who Sidious defeated).

Could Revan beat Vader?

Revan, on the other hand, has killed countless enemies both during his Jedi and his Sith time with his lightsaber. ... So, there you have it: All in all, Revan would beat Vader if you consider their different skills and talents.

Is revan the most powerful?

Revan was the most powerful warrior of his era, not counting Vitiate whom they would never even see as his plans were hundreds of years in the future.