God is a villain from Demon Lord Dante, Devilman and Devil Lady.
Demon Lord Dante
In here he was an evil space being who demanded that the humans living on Earth worship him. When they didn't, he torched their cities, inadvertently turning the entire human race into demonic beings by having God's energy merge them with various objects (the main character merges with a jet plane and dinosaurs to turn into a giant demon), and split himself up into pieces and inserted himself into apes, becoming modern man as a result. He further becomes even more of a bastard when it is revealed at the end that the entire war between God and demons was done on purpose just because it was entertaining to him.
As the Angels descend upon the Earth they are suddenly attacked by a mass armada of Demons led by the traitor Satan who proceeds to butcher the Demons. The surviving Angels group together and summon God, The two battle and Satan apparently loses and is sent into a purgatory along with demon kind. Thousands of years later not long after Zennon's speech to the world a demon named Medok possess the president of the USSR and planned to launch a barrage of nuclear missiles to destroy much of the world, however this is averted when God Turns the entire continent into salt, evaporating everything human or demon alike, simply because God was curios as to was going to gain control over Earth in the final fight between Akira Fudo and Satan.
AMON: The Darkside of Devilman
In here it's revealed that God has put the entire world into a time loop so all humans and demons live and die for nothing over and over, just to make Satan suffer the loss of his/her beloved repeatedly for all eternity.