Well, Superman's super hearing might be able to detect magic being cast from a long distance. This could give Harry and his friends an early warning of approaching danger. In terms of Harry's magic, a Patronus charm could potentially be used to protect Superman from certain dark magic attacks. The Patronus, being a positive magical energy, might surround Superman and act as a shield. And Superman's heat vision could be used to melt through magical ice or other obstacles that are created by dark wizards. At the same time, spells like the Imperius Curse might not work on Superman because of his strong will, which is similar to his resistance to mind - control in his own world.
In a more complex interaction, Alita's ability to interface with technology could be used to enhance Superman's powers or protect him from certain threats. For instance, if there was a villain using some sort of electromagnetic pulse to disable Superman, Alita could use her own technology to create a shield around him. And Superman's X - ray vision could help Alita in her investigations, like finding hidden mechanisms in a complex mechanical structure she is trying to understand. Their powers would create a unique synergy that would make for an exciting crossover fanfiction.
Aquaman's ability to control the sea could be used to create massive water - based defenses around Hogwarts. In return, Harry could use magic to give Aquaman the ability to breathe air indefinitely when he's on land for extended periods. Their powers could also combine in a more offensive way. For instance, Harry could use a levitation spell on Aquaman while he's in the water, allowing Aquaman to attack enemies from above the water surface with his enhanced speed and strength.
In a fanfiction scenario, Superman's ability to fly could give Naruto a new perspective on combat. Naruto could learn to use the airspace more effectively. He might even develop new jutsu that are based on aerial combat, inspired by Superman. And Superman could learn from Naruto's ability to sense chakra. This could help him detect hidden threats or enemies that are using some form of energy cloaking device in his own world.
Superman has super strength, flight, heat vision, etc. X - 23 has enhanced strength, speed, and her claws. If they were in a fight together, Superman could use his flight to gain an aerial advantage and X - 23 could use her speed to quickly move around on the ground. His heat vision could be used to blast enemies from a distance while she could use her claws for close - combat.
Well, Harry's magic is based on spells and the use of a wand. Hades' power is more about controlling the underworld, death, and the souls there. Persephone has power over nature, especially in relation to the underworld. If they were in a situation together, Harry's magic could potentially be used to protect the living from any threats that Hades' underworld - related powers might pose. For example, if some undead creatures escaped the underworld, Harry could use defensive spells.
Well, Harry's magic could be enhanced by Jean's telepathic influence. For example, if he's in a tough battle against a dark wizard, Jean could use her mind - reading ability to anticipate the enemy's moves and relay that information to Harry telepathically, allowing him to better use his spells. And Harry could use his magic to protect Jean from physical harm when her telekinesis is occupied elsewhere.
Well, Harry's magic is very structured within the rules of the wizarding world. Rachel's powers, on the other hand, are more related to her emotional state. If they were in a story together, perhaps Harry could use his magic to help Rachel control her powers when she's in a highly emotional state. For example, he could cast a spell to calm her down so that her powers don't go out of control.
Pietro's super speed could enhance Harry's ability to quickly move around Hogwarts during a battle or while searching for something. For instance, if Harry needs to reach the Room of Requirement in a hurry, Pietro can carry him there in an instant.
The magic in Harry Potter and the demigod powers in Percy Jackson could interact in really cool ways. For example, a wizard's spell of protection could be enhanced by a demigod's aura of strength. If a demigod was in a fight at Hogwarts, a wizard could cast a spell to make the demigod's weapon more powerful, like making Percy's sword glow with an extra magical edge.
Harry Potter's power as the Master of Death gives him a certain control over life and death. Aphrodite's power is centered around love and beauty. Their powers could interact in a way that when Harry faces a situation where a character is on the brink of death due to a lack of will to live (perhaps because of a broken heart), Aphrodite could use her love - based powers to revive their will, and then Harry could use his power over death to heal any physical ailments. For example, if a wizard has been cursed and is dying while also losing the will to fight, Aphrodite could make them feel love again, and Harry could reverse the curse's deathly effects.