God is an antagonist in the Spawn series who, despite his name, is not truly the supreme being of Spawn's cosmology (that title belongs to the Mother of Existence who is also known as the Man of Miracles or M.O.M. for short) - he was imprisoned alongside his cosmic twin brother, Satan, for many years to protect humanity from their destructive feud yet was reborn in recent times alongside Satan to renew their endless war.
In the cosmology of Spawn, the being humanity has labelled God is in reality one of an infinite number of beings created by the Mother of Creation to safeguard the worlds of the universe. However, a problem was formed when the Mother Of Creation gave Earth to 2 young twins named God and Satan. These two entities despised one another yet did not have the power to truly destroy each other - instead, they fought endlessly, causing vast destruction in the process.
God created humanity in his image only for Satan to grant them free will, which caused the two to war further and endanger humanity as they became obsessed with obtaining human souls. Seeing humanity as unique, the Mother Of Creation acted on their behalf and imprisoned both God and Satan so that humanity would have a chance to evolve free of the constant warring of her 2 sons, who she had began to see as disappointments.
However, the Mother of Creation could never bring herself to imprisoning her children forever, as they were still her offspring regardless of their constant fighting. Thus, she gave them new life as two human twins, hoping that by having them live amongst humanity, the two entities would finally change their ways.
Sadly, the Mother's plan failed and the two began fighting again, and the situation became critical when the powerful seraph known as Zera (a being so terrible she was feared by both Heaven and Hell) returned God to his former glory by giving him back his full memories.
After these events, God and Satan wasted little time in gathering their armies, and launched the biblical Armageddon. However, Spawn interfered after being granted the power of a God himself - as the empowered Spawn laid waste to their armies, God and Satan worked together for the first time to oppose him, but Spawn used his power to strip the world of all life - ending the conflict in an instant, but in the process, reducing Earth to a wasteland.
With this deed done, the Mother of Creation once again arrived and denounced her children, yet despite her warning, Spawn requested that God and Satan be granted their full powers back, and she honored his request. God, now back to his true form and power, prepared to face Spawn again alongside Satan, but was denied the fight as Spawn simply opted to walk away - already depressed over the many deaths caused due to the conflict.
However, God and Satan simply combined their powers on Spawn when he turned his back on them, and obliterated him - the Mother explained to God and Satan that they were truly her most disappointing creations and by killing Spawn, they had destroyed the last humanity left on Earth, thus depriving themselves of the very thing they had spent an eternity warring over. She then left the two beings alone on a barren world.
God stood with Satan on the empty Earth, and for a brief moment, the two felt remorse. However, when Satan tried to talk to God, madness descended once more and the two deities fought - unable to end the feud that had cost them everything. Spawn would then go on to remake the Earth in his image, with God and Satan both banished from it so as not to cause anymore destruction.
In the "Endgame" story arc, God is mentioned once again as being back in Heaven, how he escaped his fate following Armageddon is unknown and it has yet to be established if he is yet aware of the new world where humans have been reborn.
Powers and Abilities
God is virtually a powerful being in heaven, rivaled only by Satan in power and surpassed only by the Man of Miracles (who is also known as Mother of Creation / Existence) - this puts him more on a power-scale of a powerful deity than the traditional monothestic view of God since he is not fully omnipotent nor was he shown as omniscient (since he could not foretell his defeat by Spawn). Like Satan, he seemed to have a near-endless rage that was sufficient to turn planets into ash at their peak and kill the godlike Spawn after he had eaten from the forbidden fruit.