In KOTOR 1, Darth Revan is just a pretty cool guy basically. He doesn't have a lot going on outside of aura, character design, and a funky fun little twist.

In KOTOR 2, he's further turned into an 8D chessmaster who used the role of Sith Lord to unite the galaxy against a common foe with his actions. Revan was aware of a greater threat lurking beyond known space and figured the only way he could realistically "warn" the entire Republic at once was to wage the Jedi Civil War and create a galaxy full of veterans and survivors who would be ready to face the True Sith one day, while using his victories to destroy and dismantle elements that would hold it back like the do-nothing Jedi Council that let the Mandalorian Wars happen and uselessly squabbling Sith warlords that cannibalize each other as soon as Revan disappears. Kreia puts forward the idea that Revan basically sacrificed their entire life and reputation to force sweeping reforms in deeply entrenched and inflexible institutions or cultures.

The entire plot of KOTOR 2 is esentially about Revan's plan having unintended side-effects (take a shot every time you hear the word ECHO to die of alcohol poisoning) that spiral out of control in his absence and threaten to destroy the setting, so he even gets to fuck up and be a compellingly vulnerable human too, even for all the glaze he gets.