Ibac is an enemy of Captain Marvel.
Background Information
Two-bit crook Stanley "Stinky" Printwhistle planned to derail a train and loot the wreckage. He was thwarted by Captain Marvel and was falling to his doom when he was saved by Lucifer. Lucifer offered Printwhistle the chance to wield evil power in exchange for his soul, and Printwhistle agreed. By saying the word "IBAC," he would be engulfed by green fire and changed into a monstrous being with the powers of historical evildoers: Ivan the Terrible, Cesare Borgia, Attila the Hun, and Caligula. Despite his powers, Ibac was defeated, although he returned to tangle with Captain Marvel many other times.
Since he never defeated Captain Marvel, Printwhistle was never forced to surrender his soul to Lucifer, and after realizing the futility of his situation even gave up crime and became a street cleaner. However he was still weak-willed, and could sometimes be forced into changing back into Ibac by other criminals.
Powers
Divine Empowerment
While his powers are somewhat hard to quantify, Ibac was generally shown to be less strong and resilient than Captain Marvel and was usually at a disadvantage in direct fights.