seriously what is Mordo thinking?

He lost his faith, but that doesn't mean he's becoming a villain, maybe an anti-hero. He didn't kill the guy at the end, just took his magic healing, so he isn't a murderer. He plans to embark on a journey to neutralize sorcerers who are using their powers for perverted purposes - according to his point of view. But I think Strange might be able to talk him out of it. I would hate to see Mordo dying or something, I like the actor and I liked the character.

I once told a man to go screw himself! Can you even imagine?! - Kilgrave

I agree. Can't help but think of the primary criticism of Marvel films: crap villains.

I've re-watched the film a few times, and the term 'whiney-beeyatch' comes to mind. 'Dude, get over yourself.' (Or, in the words of The Ancient One, 'It's not about you.')

Bad writing.

Ya it seemed super contrived that he was so willing to walk away that easily.

He wasn't thinking... he was following his heart. :) As I always say, they can save the explanation for the sequel. It was not a total mystery to me why he went bad, although an answer to this should be given. But let's not forget this was a post-credits scene, it's supposed to leave us asking questions.

Let's face it. The main villain of the movie was exactly like Mordo in the original comics. The guy named Mordo is Mordo in name only. Mordo was never Doctor Strange's friend in the comics. I still like the film but it does bother me they completely changed things around for no reason.

I don’t think he’s a full blown villain just yet. Otherwise, he would have tried to kill Strange and Wong right away. He is dissillusioned right now.