Azazel's popularity and importance towards the franchise even led him to be the main antagonist and the analogue to Lucifer in the anime adaptation, as the "Yellow-Eyed Demon," in reference to the nickname he had in the original first two seasons.
In the TV show "Supernatural," the strongest demon is often considered to be the demon named Lucifer. Lucifer is one of the most powerful beings in the show and is portrayed as a major antagonist.