Its already been explained pretty much. He's one of the four Aspect Lords, the Gods of Gods, the first four beings that ever existed. Beings who maintain multiple universes and infinite timelines and are the centerpiece of all of existence. Without one, existence ceases. It would only be logical that such important beings would also be incredibly powerful, more so than any other God-being from any Universe.
i think the second panel is missing a word in between."he relinquished control of his 3 universes to control.Instead,all 12 makai realms"??does this mean he controlled the 12 makai realms instead of his 3 universes or does it mean he would accept challenges to his throne from these 12 makai realms??
So okay reading the comments seems to suggest that no villain will be as strong as Aladjinn and that if he's killed everything dies so why have him as the 2nd villain if he's stronger than any other villain that comes along the story? because after beating him none of the others should seem that much of a threat when our heroes have faced the most powerful being in existence of course he isn't fully powered yet, but as it's always in DB the villain gets his full power back at some point.