Lord Voldemort would also be a contender for the most powerful. His dark magic is extremely potent. In the Rosario Vampire world, his ability to control and manipulate could give him an advantage. He might try to use the vampires and other creatures for his own dark purposes, and his powerful curses could cause a lot of chaos.
Albus Dumbledore would likely be very powerful. His vast knowledge of magic and his strategic mind would give him an edge. He could probably outwit most of the Rosario Vampire characters with ease. Plus, his powerful spells like the Patronus Charm could be very effective against the various threats in the Rosario Vampire world.
Tsukune from Rosario Vampire and Harry Potter would be an interesting crossover. Tsukune is a human in a world full of vampires and other supernatural beings. If he were to meet Harry, he could learn a lot about a different kind of magic and how to use it to his advantage in his own world. Also, Harry could learn about Tsukune's tenacity in dealing with the challenges in his world.
Hermione and Tsukune Aono could be another great pairing. Hermione's thirst for knowledge would match well with Tsukune's curiosity. Tsukune, being a human in a vampire school, has had to adapt and learn quickly, much like Hermione in the wizarding world. They could exchange their knowledge about their respective worlds, and together they might come up with unique solutions to problems that arise in the crossover story.
It's likely that Ben with the Omnitrix would be one of the most powerful. He has access to a wide variety of alien forms, each with their own unique abilities. For example, Heatblast could deal with cold - based threats in the Rosario Vampire world, and XLR8 could outrun any fast - moving vampires or enemies. However, some of the powerful vampires like Alucard in Rosario Vampire also have incredible strength, speed, and magical abilities. So it could be a close call between Ben in his most powerful alien forms and the top - tier vampires.
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.
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.
In a crossover, it could be argued that Harry Potter is the most powerful. His magic can do things that are beyond Batman's physical capabilities. For example, he can apparate, which is a form of teleportation, and he can use spells to immobilize or defeat his enemies. While Batman is a formidable fighter and detective, he doesn't have the ability to counteract magic directly. However, Batman's strategic mind might be able to find ways to work around Harry's magic, but in terms of raw power, Harry has the edge with his magic.
It's hard to say who would be the most powerful. Harry Potter has his powerful magic, like the Patronus charm and the ability to use the Elder Wand. However, Wonder Woman has her superhuman strength, speed, and combat skills, not to mention her Lasso of Truth. In a way, it depends on the situation. In a magical battle, Harry might have the upper hand, but in a physical combat, Wonder Woman would likely be dominant.
I think Harry Potter himself would be very powerful in this crossover. He has the experience of fighting dark wizards and his magic skills. If he was in the MHA world, he could use his magic to enhance his physical abilities like the characters with quirks. His ability to resist the Imperius Curse and his knowledge of defensive magic would give him an edge over many MHA villains.
Some might argue that the Scarlet Witch from the Marvel universe (which is related to Captain America's world) could be very powerful in this crossover. Her reality - warping abilities could have a huge impact on the wizarding world. But then again, the wizards have their own ways of protecting their world from such powerful threats, like powerful wards and ancient spells that have been passed down for generations.