It could be Harry Potter himself. He has defeated Voldemort, one of the most powerful dark wizards. His ability to perform advanced magic like the Patronus charm and his experience in facing great evils would give him an edge. He could also learn from the Olympian magic and become even more powerful.
Well, Raiden from Mortal Kombat might be a strong contender. He is a thunder god with incredible powers. In a crossover with Harry Potter, his ability to control lightning could give him an edge. He could use his powers to disrupt the magic of wizards or directly attack them. And his immortality would make him a difficult opponent to defeat, even against the most powerful wizards.
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.
In the context of the Harry Potter universe, Harry Potter himself could be very powerful. He has the power of love and friendship on his side, which has been shown to be a great strength in the series. He also has his own magical abilities that he has honed over the years. If he were to combine his magic with the knowledge of the Avengers about Ultron, he could be a formidable force against any threat.
Arcturus Mengsk from Starcraft could be very powerful in this crossover. He is a master strategist. In the crossover, he could use his political and military acumen to manipulate the wizarding world. He might try to gain control of Hogwarts or use the wizards' magic for his own imperialistic goals. His ruthlessness and intelligence would make him a formidable force, especially when combined with Starcraft technology.
It's really hard to say. Harry Potter has his powerful magic from Hogwarts and his connection to Voldemort which gives him a certain power boost. But in the DxD world, characters like Great Red are extremely powerful. If Harry was able to combine his magic with the power of a Sacred Gear, he could potentially be a very strong force. However, characters like Sirzechs Lucifer also have a vast amount of power. So it could be a toss - up depending on how the crossover is written.
However, Harry Potter himself could also be very powerful in this crossover. He has a lot of experience with dark magic and defeating powerful villains. When combined with the unique magic of SVTFOE, he could become even more powerful. For example, he could use his knowledge of the Deathly Hallows and combine it with Star's Butterfly magic to create new and unbeatable defenses or attacks.
I think it would be Dumbledore. He is extremely powerful in the Harry Potter world. His wisdom and magical abilities are off the charts. In Westeros, he could use his powerful spells to influence events, protect people from danger, and perhaps even find a way to bring peace to the war - torn land. His ability to see into people's minds would also give him an edge in the political games of Westeros.
It's hard to say. Harry Potter has his powerful magic, like the ability to cast powerful spells and his connection to Voldemort which gives him certain powers. But Jack Sparrow has his wits and his charm. He's able to talk his way out of almost any situation and has a great deal of experience in combat and survival. So, it really depends on the situation. In a straight - up magical battle, Harry might have the upper hand, but in a situation where negotiation or outsmarting the enemy is key, Jack could be the more powerful one.
It's hard to say. Naruto has his huge chakra reserves and powerful jutsu. But Harry has the power of love and some really strong spells. However, I think Dumbledore would be very powerful in this crossover. He has great wisdom and extremely powerful magic. He could probably figure out how to use Naruto's chakra to his advantage if they were on the same side.