Revan’s a really hard character to really understand fully because a lot of what he is relies on how one plays through Knights of the Old Republic. As mentioned previously, he rebelled against the Jedi Council to fight the Mandalorian War with Malak before he was turned to the dark side. Malak eventually tried to kill him and usurp his power.
What happens next is fascinating: the Jedi save Revan’s life and replace his memory with those of a loyal Republic soldier and upstanding, obedient Jedi. It’s not Clockwork Orange level forcing people to become good by morally dubious means, but it does open the door for philosophical questions about what the Jedi chose to do.
Revan also falls in love with Bastila Shan, the Jedi who saved him. Witnessing his rise, fall, and rebirth throughout games and books give him one of the most complex arcs of any villain in the universe. He is forced to be evil and forced to be good, and only in the end does he find himself.
The final battle between him and Malak is very well done, and the short conversation they have about one choosing to return to light and one staying in darkness is a really good one. Unlike a lot of the villains, especially the Sith, Revan is not devoid of humanity. He seems like a very normal person. He feels guilt, love, doubt, shame, confusion and all the other feelings that befall characters that are interesting, whether they are heroes or villains.
On top of his great character development and purpose in the universe, he is a very powerful and awesomely designed character. He just screams bad guy.
Does it look like his design basically became Kylo Ren? The answer is yes. If Kylo is half the character Revan was, everything should be fine.
Next: 3. King of the Bounty Hunters