If Batman had Superman powers in fanfiction, he would be an unstoppable force. He could use his detective skills combined with super strength, flight, and heat vision. Gotham would be a much safer place as he could quickly stop crimes across the city without relying on his gadgets as much. He might even be able to take on more global threats, which would be a huge change from his normal focus on Gotham's underworld.
If Naruto had Superman's powers in fanfiction, he would be nearly unstoppable. His existing ninja skills combined with Superman's flight, super strength, and heat vision would make him a formidable force. He could easily defeat his enemies in the Naruto universe, like Orochimaru or Pain, without breaking a sweat.
Superman's powers come from his alien physiology. He's from the planet Krypton, and its different environment and genetic makeup gave him superhuman abilities like super strength, speed, and the ability to fly.
He could develop the ability to combine his chakra with Superman's powers. For example, he might be able to use his Rasengan while flying at super - speed. Or he could infuse his chakra into his heat vision to make it even more powerful.
In a Naruto - Superman powers fanfic, perhaps Naruto gets some of Superman's powers accidentally. He struggles to control the new powers like heat vision and super speed along with his own ninja abilities. Superman, on the other hand, discovers he can use chakra in a limited way and they both have to figure out how to use these new combinations of powers effectively.
He might become more confident. Batman is already a confident character, but with Superman's powers, he'd have a new level of assurance. He could take on any threat without hesitation.
Deku's One For All power could be seen as a sort of super - strong magic in the Fairy Tail universe. It could be that he has to learn to control it in a different way, like using the Fairy Tail guild's training methods. Maybe he'd have to combine it with some form of Fairy Tail magic to make it even more powerful.
His powers would be seen as extremely abnormal at first. People in the cultivation world are used to powers obtained through cultivation, while Superman's are innate.
Superman's powers would have a huge impact. His super - strength could make him the strongest member of the team, and his flight would give the Avengers an added dimension in battles. His heat vision could be a powerful weapon against enemies.