Dumbledore. He has the wisdom and experience to handle the immense power of the Infinity Gauntlet. He could use it to restore balance in the wizarding world in ways that others might not think of. For example, he could use it to heal the long - standing divides between different wizarding communities, like the pure - bloods and the Muggle - borns, in a more permanent way.
He might find it in a hidden chamber in Hogwarts. Maybe it was left there by a powerful wizard from long ago who had some connection to other universes.
He would probably become extremely powerful. He could use the Infinity Stones' powers to defeat Voldemort in an instant. For example, the Power Stone could enhance his magic to an unimaginable level, and the Time Stone might allow him to go back and prevent bad things from happening in the wizarding world.
All Might could be a likely candidate. He's the symbol of peace in the My Hero Academia world and has a strong sense of justice. If he were to get the Infinity Gauntlet, he would probably use it to protect the world and keep the balance between heroes and villains. His already incredible strength combined with the power of the Infinity Gauntlet would make him nearly unstoppable.
The plot might involve Harry accidentally stumbling upon the Infinity Gauntlet in the Room of Requirement. As he tries to figure out what it is, he discovers its immense power. However, the Ministry of Magic wants to use it for their own gain. Harry has to decide whether to keep it safe from the Ministry or use it himself to finally defeat all the dark forces that still lurk in the wizarding world.
It would change drastically. He'd be much more powerful than before. He could easily end the war against Voldemort.
Harry Potter himself would be very interesting. Combining his wizarding skills with Kryptonian powers would make him an extremely powerful character. He could be the bridge between the two worlds and use his new powers to protect both the wizarding world and the world of Kryptonians on Earth.
He could gain the power to control time, which would be really useful in the wizarding world. He could go back and prevent some of the bad things that happened, like the death of his parents.
Hermione Granger would also be a likely candidate. Her thirst for knowledge and her extensive research in the library might lead her to discover ancient texts about the Infinity Stones. Then she would go on a mission to find them, using her intelligence and magical skills to track them down.
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.
Harry and Elsa would be a very interesting pairing. Harry, with his experience in facing dark magic, could offer Elsa a new perspective on her powers which she has always seen as a curse. And Elsa, with her ice powers, could show Harry a different kind of magic that he's not used to in the wizarding world. Another interesting pairing would be Ron and Kristoff. They both have a simple - minded charm and could get into all sorts of funny situations together, like getting lost in the Forbidden Forest or on the mountains in Arendelle. Also, Hermione and Anna would be great. Hermione's intelligence and Anna's determination would make them a formidable duo as they try to solve problems in both their worlds.