Plus Revan killed a bunch of Mandalorians, nearly to the brink of extinction, and then conquered a good chunk of the Republic, turning lots of Jedi along the way. If the Jedi hadn't launched a last-ditch suicide run on his flagship he would have conquered the entire Republic. And after he then saves the Republic, he does what he planned to do with the conquered Republic and confront the True Sith somewhere out in the Unknown Regions, except he does it all by himself, leaving Carth, Bastila, HK-47, and B4-D4 behind.
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Palpatine did conquer the whole republic
And created the Galactic Empire
Palpatine was a sith lord in control right under the noses of a thousand jedi
I doubt revan had the kind of power for that kind of concealment for that long