One possible plot could be that Thor somehow gets transported to the wizarding world. He might initially be confused by the magic there as it's different from his Asgardian powers. Harry Potter and his friends could be intrigued by Thor and his hammer. They might team up to fight a common enemy, perhaps a dark wizard who has somehow got hold of some Asgardian artifact and is misusing its power.
One possible plot could be that Thor ends up in the wizarding world of Harry Potter. Maybe the Bifrost malfunctions and he lands near Hogwarts. He could be mistaken for a very powerful wizard at first. Then he teams up with Harry Potter and his friends to fight against a new dark threat that is using both magic and some form of Asgardian - like power. Thor could teach the wizards about Asgardian combat and they could teach him more about the nuances of magic.
A powerful dementor - like being that has been corrupted by Asgardian dark magic. This entity could be draining the life force of both wizards and Asgardians. It would be up to Thor and Harry Potter to find a way to stop it, as it poses a threat to both of their worlds.
It could be Loki. Since he has a knack for causing trouble, he might find a way to cross over to the wizarding world. He could manipulate the dark wizards and use their magic for his own devious plans. Maybe he wants to steal the Philosopher's Stone to gain immortality and use it to take over Asgard as well.
Well, Harry Potter would probably become an even more powerful wizard. Thor's combat skills and physical strength could be incorporated into Harry's magical abilities. Maybe he'd be able to cast spells while doing some of Thor's epic leaps and strikes.
Well, Thor is a very confident and powerful character. He might be initially a bit baffled by the wizards and witches at Hogwarts. Harry, on the other hand, would be in awe of Thor's strength and abilities. Thor could probably teach Harry some physical combat skills, while Harry could introduce Thor to the subtleties of wizard magic like apparition.
One idea could be that Thor somehow ends up at Hogwarts. Maybe he's on a mission in the wizarding world and his Asgardian magic interacts in strange ways with the magic of Hogwarts. For example, his lightning powers could cause some chaos during a Potions class when it accidentally zaps a cauldron.
Yes, there are likely some out there. Fans often create crossover fanfics that combine different universes like 'Hitman' and 'Harry Potter'. These can be really interesting as they blend the magic and mystery of 'Harry Potter' with the stealth and assassin - like nature of 'Hitman'.
One idea could be that Megara, with her sharp wit and street - smart nature, finds herself in the wizarding world of Harry Potter. She could team up with Harry and his friends, using her own unique skills to help them out in a dangerous situation, like facing a new dark wizard threat.