
Abraxas is a cosmic-entity in the Marvel universe who was released when Galactus seemingly died, whose main opponents were the Fantastic Four as well as a number of cosmic-heroes/beings from across the Marvel universe - although due to the vast nature of his power it could be argued Abraxas has the honor of being the opponent of practically every being in Marvel - hero and villain alike.
Currently, Abraxas is imprisoned, but he patiently awaits to be released.