DC Comics Version
Also called the Lord of the Flies, Beelzebub is one of the prime devils inhabiting the eternal realm of suffering. He has dominion over decay and decomposition, and has existed since the creation of death itself. Consequently he uses the authority that comes with age to push himself into the thick of any political discussions within hell's hierarchy. For a time, Beelzebub ruled hell with Lucifer and Azrael as a triumvirate, but returned to his former station when God sent the angels Remiel and Duma to oversee the infernal realm.
Later, Beelzebub assumed a humanoid shape and crossed paths with the Earth based heroes Kid Eternity and Supergirl. He continues to spread his evil throughout the universe and will likely exist until the end of time.
Beelzebub Manga Version
Often referred to instead as the Great Demon Lord in the successful Beelzebub manga, Beelzebub was presented still as one of the seven Princes of Hell (called the Seven Deadly Sins), but more importantly he is technically Beelzebub III, and it is his son Beelzebub IV who is the titular character of the series.