We're talking evil.... Lord Revan wipped out the entire galaxy and has a Dark pwer emitter that actually corrupts good. No one can resist the star forge, along with it being a factory that builds star destroyers and clones armies of sith... not to mention the factory and battle station regenerates and is powered by the very thng it creates! evil! Darth Revan usesed and wipped out everyone he knows, all who are his friends dies. Alone he is invincible because he channels life from anyone near him. Seperoth like you said is just insane and apparently immortal, but through seizing it from someone else magically or whatever... Revan was born into total darkness... using the light for his own power.
yeah squar really kicked them selves in the face with Sephiroth, they made him insanley powerfull but he was the villian so he has to lose. even with the "weakening" of Seph due to holy, and Ares, it was still kinda odd seeing him lose ((even if it was just a projection or however that theory goes))
but in Kotor you play the villian? isnt he that guy with half a mask?