I would question why is that character more powerful than Superman. And would not get a satisfactory answer.
He's basically an Imp. He's an extradimensional being from a "Higher Level" Dimension than ours who has immense power over beings in this Dimension and usually can only be defeated by rules he sets for himself. Usually by defeating him in games he wants to play or making him say his name backwards.
Imagine the "Q" equivalent for Superman. Some stories imply he's more powerful than Darkseid
He could annihilate Superman anytime he wants, but he enjoys anything amusing so he always just leaves when the challenge/game is won or Superman gets him to say his name backwards because he honors the limit he puts on himself
Oh, and Superman isn't "vulnerable" to magic like it's his Kryptonite. It's just that magical things bypass his capabilities the way they bypass everyone's capabilities due to the inherent nature of magic.