Probably the Joker. It's a really wild idea. Harry Potter being raised by the Joker would mean he'd grow up in a world of chaos and madness. He'd have to constantly question his own moral compass. His magic might be used in really strange and unpredictable ways. For example, the Joker might make Harry use his magic for pranks that are actually quite cruel, and Harry would have to figure out how to use his magic for good in such an environment.
Lex Luthor could also be an unexpected choice. He would see Harry's magic as a potential weapon or a tool for his own gain. Harry would be exposed to Luthor's scientific and devious mindset. His magic might be studied and manipulated by Luthor. But at the same time, Harry could learn some valuable skills from Luthor in terms of strategy and understanding technology, which he could then combine with his magic in unexpected ways.
I think Darkseid would be the most unexpected. Imagine Harry Potter being raised in Apokolips. He would have to adapt his magic to survive in such a harsh and evil - dominated place. His magic could potentially be a threat to Darkseid's rule, or he could learn some dark magic - like powers from Darkseid's regime, which would completely change his character and the way he uses magic.
The Hulk and Neville Longbottom. It seems really odd at first because the Hulk is this big, powerful brute and Neville is often seen as a bit of a clumsy underdog. But Neville has a lot of hidden courage. In a battle, the Hulk's brute strength combined with Neville's new - found confidence and knowledge of magic could be a really unexpected and powerful alliance.
I think Hermione and Superman would be an interesting pair. Hermione is all about knowledge and learning, and Superman, with his alien origin and super - intelligence, could share a lot with her. They could exchange ideas about their respective worlds, and Hermione might even find a way to use magic to enhance Superman's powers or help him in some way.
I think Michael Corvin could be an interesting crossover character. He's a hybrid in the Underworld series, which means he has a unique set of abilities. In the Harry Potter world, he could be seen as a strange new kind of magical being. He might be able to help the wizards understand different types of magic that are more physical and instinct - based like his own. Also, his journey of self - discovery in the Underworld could be paralleled in the wizarding world as he tries to find his place among the wizards and witches.
One possibility could be centaurs. Centaurs are intelligent and have their own code of ethics. They could raise Harry with a deep understanding of nature and the stars, which would give him a different kind of wisdom.
In this fanfiction, Harry's powers would likely be shaped by the cutthroat nature of the DC villains. He might learn to use magic more aggressively, perhaps even using it to intimidate or control others. For instance, instead of using a simple stunning spell in self - defense, he could use it to subdue someone for his own purposes. His magical development would be less about following the rules of the wizarding world and more about achieving his own, possibly villainous, goals.
Harry would probably be more attuned to dark magic. His upbringing by Satan would expose him to different forms of magic and he would have a different understanding of power. He might be more ruthless in achieving his goals and less concerned about the consequences for others. For example, in the original series, Harry was always worried about the safety of his friends, but in this fanfiction, he might use his friends as pawns if it served his purpose.
Hermione would be really interesting. She could bring her intelligence and knowledge of magic to the iCarly crew. Imagine her helping Freddie with his tech projects using magic, or teaching Carly and Sam some basic spells. It would be a great contrast between the magical and Muggle worlds.
It's hard to say for sure, but Alucard has a strong case. His vampiric powers are extremely formidable, including his ability to regenerate, his superhuman strength, and his vast array of weaponry like the Casull and the Jackal. He also has centuries of combat experience. However, in the wizarding world, Dumbledore is an incredibly powerful wizard with a deep understanding of magic. He could potentially find ways to counter Alucard's powers, like using powerful spells of binding or banishment.
Some might think that a WWE superstar like The Undertaker could be the most powerful. His in - ring presence is so intimidating. If he were to somehow gain some magic abilities, like being able to control the dark elements similar to some dark wizards in Harry Potter, he could be truly unstoppable. He already has a reputation for being 'undead' in the WWE, which could be enhanced with some dark magic elements from the Harry Potter world.
It could be Aquaman. He is so different from the wizards in the Harry Potter universe. His fish - like abilities and his role as a king would make for some great interactions with the Hogwarts students and professors. He could teach them about the ocean and its secrets, while also being amazed by the magic of wands and potions.