Harry and Tsuna would be a great pairing. Harry has the weight of saving the wizarding world on his shoulders, and Tsuna is constantly growing into his role as the Vongola Decimo. They could learn from each other's experiences of facing great challenges and finding their inner strength.
Hermione and Tamaki would make for a unique pairing. Hermione's intelligence and studiousness contrasted with Tamaki's flamboyant and somewhat naive personality. Tamaki could introduce Hermione to the world of charm and social graces, while Hermione could help Tamaki with his studies if he were to be in the Hogwarts environment.
I think Rock Lee and Gokudera would be a fun pairing. Rock Lee's extreme dedication to training and his unique fighting style would surely amaze Gokudera. Gokudera, in turn, could introduce Rock Lee to the power of the Dying Will Flame and how it can enhance combat abilities. Also, Kakashi and Reborn would be an interesting match. Kakashi's vast experience and intelligence combined with Reborn's shrewdness and unique training methods would make for some great interactions.
Ron and Angel Dust. Ron is often the more down - to - earth and food - loving character in Harry Potter. Angel Dust, on the other hand, is flamboyant and has a wild side. Their differences could lead to some really comical and also heartwarming interactions. Ron could introduce Angel Dust to some wizarding world food, and Angel Dust could show Ron some of the unique and fun aspects of Hell's nightlife, while also learning about loyalty from Ron, which is something he might lack in his own life.
Definitely Harry Potter and Spider - Man. Harry could teach Peter about the magical world, like how to use a broomstick. And Peter could show Harry how to use his web - slingers in a more creative way in combat. They're both young heroes with a strong sense of justice, so they'd get along well.
Harry and Naruto would be an obvious and very interesting pairing. They are both the main heroes in their respective stories, so seeing them interact, share their experiences, and learn from each other would be great. Hermione and Sakura could also be a fascinating pair. Both are intelligent and strong - willed female characters. Hermione could teach Sakura about complex magic theories, while Sakura could show Hermione some of her medical ninjutsu skills.
Ron Weasley and Issei Hyodo could also be a fun pairing. Ron's laid - back but brave nature along with his Weasley family magic could interact interestingly with Issei's determination and his unique Sacred Gear abilities. They might start off as rivals, but then become friends as they face common enemies in the combined universe of the fanfiction.
Harry Potter and Aladdin would be a very interesting pairing. Harry is used to the more structured magic of the wizarding world, while Aladdin has his own unique magic style. They could learn a lot from each other. Another great pairing could be Hermione and Morgiana. Hermione's intelligence and thirst for knowledge could be paired well with Morgiana's strength and loyalty.
Harry Potter and Luffy would be an amazing pairing. Harry's serious and sometimes brooding nature combined with Luffy's carefree and positive attitude would create a great dynamic. Luffy could also teach Harry about having more faith in his friends and believing in himself without relying so much on magic all the time.
I think Harry Potter and Yuuichiro Hyakuya would make an interesting pairing. Harry is used to fighting against dark magic and Yuu is a fighter against vampires. They could share their combat experiences and learn from each other. Another interesting pairing could be Hermione and Shinoa. Hermione's intelligence and Shinoa's combat skills could combine in interesting ways when they face challenges together.
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.