Mongul is a fictional supervillain considered one of the strongest, yet least known, of Superman's enemies.
Mongul first appeared in the pages of the DC Comics Presents comic book series, in stories written by writer/artist Jim Starlin. It is apparent that Starlin created Mongul as a version of his most famous villain character, Marvel Comics' Thanos, for use in the DC Universe (which is ironic, considering that Thanos originated as an imitation of DC's Darkseid). However, Mongul is probably best known for his part in the story "For the Man Who Has Everything" by British writer Alan Moore. "For the Man Who Has Everything" appeared in a Superman Comics Annual. Some of the Mongul stories (including "For the Man Who Has Everything") have been adapted into episodes of the Justice League animated series.
In the comics, Mongul was originally the tyrannical ruler of his own alien race (who, like him, are yellow-skinned humanoids.) He was eventually deposed by a revolution, and Mongul swore he'd reconquer his subjects. To this end he sought the most powerful weapon in the universe: the artificial planet Warworld. To activate it, however, he needed a "key" device, which was under the care of the Martian Manhunter. Mongul kidnapped three of Superman's friends (Lois Lane, Jimmy Olsen, and Steve Lombard) to force the hero to get the key for him. Superman fought against and defeated the Manhunter and obtained the key. In the subsequent scuffle, the Manhunter rescued Superman's friends, but Mongul escaped with the key.
Mongul activated Warworld and linked his mind directly to its controls. Warworld was attacked by Superman and Supergirl, and Mongul used its superweapons against them. Almost too late, he realized that the controls' drain on his brain was too strong; however, he managed to escape just before the heroes destroyed Warworld.
Some time later, Mongul again tried to steal a superweapon; this time, it was a planet-destroying ray machine used by the empress of another galaxy to blackmail its citizens into obedience. It was controlled by the empress's crown. In a plot to obtain the crown, Mongul killed the empress, captured her brother, the alien superhero Starman, and threatened to kill him unless Starman's lover gave him the crown. He got the crown, but was attacked again by Superman; this proved to be a diversion while Starman destroyed the weapon. Again, Mongul escaped.
Desiring revenge on Superman, Mongul stole a Sun-Eater from the Controller who kept it, and tried to use it to devour the Earth's solar system. With help from the Legion of Super Heroes, the Sun-Eater was destroyed (and Superman was finally able to defeat Mongul in hand-to-hand combat).
After DC Comics decided to reboot their universe (see Crisis on Infinite Earths) the original Mongul stories were no longer valid. Mongul was reintroduced as already having obtained Warworld and having used it to create his own space empire. He entertained the empire's citizens with gladiatorial games; the champion was an alien warrior called Draaga. Mongul captured Superman for use in the games, but the hero ended up joining forces with Draaga and making Mongul flee. (Note: this version of Mongul was not stronger than Superman.)
Mongul then joined forces with the Cyborg Superman in order to gain vengeance on Superman and to try to turn the Earth into another Warworld. In the process, Green Lantern Hal Jordan's home, Coast City, was destroyed, which led to Jordan joining Superman and his allies to defeat Mongul (see Death of Superman.)
Death & Legacy
Mongul was killed by the Demon lord Neron after he refused to join forces with Neron against Earth's heroes.
Mongul, the son of the first, appeared to assist and train Superman, in preparation for the forthcoming Imperiex. He was apparently killed during the conflict, but returned to menace Hal Jordan, the newly-returned Green Lantern by using the Black Mercy on him and Green Arrow. In the meantime, he sought his sister, Mongal, to settle family squabbles. The heroes broke free and used a teleporter to transport Mongul and Mongal to their home planet. Stating family to be a weakness, Mongul punched off Mongal's head.
In the animated series Justice League, Mongul is the ruler of War World, and sends Superman to the gladiator pits of his domain. However, he is defeated, and disappears until Justice League Unlimited.
In the Justice League Unlimited adaptation of "For the Man Who Has Everything," Mongul (Eric Roberts) tricked Superman by sending him an alien parasite disguised as a birthday present. The parasite trapped Superman in a coma, while making him live an imaginary life in his mind, a life in which Krypton had never exploded and he had grown to adulthood there. With help from Batman and Wonder Woman (who had also come to give him birthday presents), Superman escaped the trance, in part with his fantasy world subconsciously and gradually subverted into a nightmare of social chaos, and trapped Mongul with his own parasite.