Another powerful combination could be Scarlet Witch and Roy Mustang. Scarlet Witch's reality - warping powers and Roy Mustang's ability to control fire through alchemy. Together, they could create massive and unique attacks. The Scarlet Witch could manipulate the fabric of reality to enhance Roy's fire - based alchemy, making it even more destructive and unpredictable.
If you combined Edward Elric and Eren Yeager, they would probably be very powerful. Edward has his alchemy skills which can be used for various things like creating weapons or barriers, and Eren has the ability to transform into a Titan. Together, they could use alchemy within the Titan form, perhaps creating stronger structures or weapons directly on the Titan's body.
It's hard to say for sure, but many would argue that Naruto could be extremely powerful. His ability to use chakra, perform various ninjutsu, and access the power of the Nine - Tails gives him a huge edge. However, characters like Thor with his godly powers and the Hulk with his incredible strength also can't be underestimated.
Thor could also be very powerful. He has his Asgardian strength and his hammer (or Stormbreaker). If he were to also gain the ability to use magic like the wizards in Harry Potter, he could be near - invincible. He could call lightning while also casting spells. And his knowledge of different realms could give him an edge in any battles that span across the combined universes.
Edward Elric would be a very interesting choice. His brash and determined personality would clash and also blend well with the Fairy Tail mages. He could learn about the different types of magic in Fairy Tail and might even try to find a way to combine his alchemy with magic. His search for the Philosopher's Stone could also take an interesting turn in the Fairy Tail universe.
I think Naruto and Alphonse Elric would make a really unique pairing. Naruto's ability to see the good in people and his constant pursuit of friendship could be a great influence on Alphonse, who has been through so much. On the other hand, Alphonse's calm and reflective nature could help Naruto think more deeply about his actions. Another interesting pair would be Sakura and Izumi Curtis. Sakura could learn a great deal from Izumi's tough - love approach to training and her strong alchemical skills. And Izumi could perhaps be inspired by Sakura's medical knowledge. And finally, Shikamaru and Scar would be an odd but interesting pair. Shikamaru's intelligence and Scar's complex view of the world could lead to some really thought - provoking discussions.
Combining Doctor Strange and Shoto Todoroki could result in a very powerful character. Doctor Strange has his mastery over magic, with the ability to create portals, manipulate time, and use various spells. Shoto Todoroki has his ice and fire Quirks. The combination would mean that this new character could use ice and fire attacks while also being able to use magic to control the battlefield. They could freeze enemies and then shatter them with fire spells or use portals to surprise opponents.
Edward Elric and Tony Stark would definitely have some interesting interactions. Edward, with his knowledge of alchemy, would be both intrigued and a bit put off by Stark's high - tech gadgets. Stark, on the other hand, would probably see Edward as a brilliant but somewhat naive young scientist. They could argue about the best way to solve problems, with Edward pushing for more 'natural' alchemical solutions and Stark relying on his tech.
Another possibility is Doctor Strange. His magic is already very powerful. If he were to gain some of the unique abilities from Ben's aliens, like the XLR8's super speed for his spell - casting, it would make him even more formidable. The power balance really depends on how the fanfiction writer chooses to blend the two universes' powers.
Some characters might feel flattered. If the fanfiction portrays them in a heroic and positive light, especially if it emphasizes their good qualities like Edward's determination or Alphonse's kindness, they might secretly feel a bit of pride and be flattered by the author's view of them.
Edward Elric is often very popular. His complex character, with his determination and the heavy burden he carries, makes him a great focus for fanfiction. Writers like to explore his emotions further, such as his guilt over his failed human transmutation attempt.