Upon his return in season 11, it was finally confirmed that he was God. His status as God and His vile nature were hinted towards Him in His first appearance when the Winchesters confront him as "Chuck", who had been writing the Supernatural book series that detailed everything that happened to the Winchesters by then.

It should be no surprise that one of the best villains on Supernatural is Lucifer, the devil himself. As a fallen archangel and the King of Hell, he holds knowledge and power that nobody else in the world could have besides God, Death, and Amara.