It's likely to be Goku. His ability to reach Super Saiyan levels and beyond gives him an insane amount of power. In comparison, even the strongest quirks in My Hero Academia seem relatively weak. Goku's combat experience and his constant pursuit of getting stronger would make him a dominant force in the merged universe.
Another possibility is Whis. If he were to enter the My Hero Academia world, his angelic powers would be almost unrivaled. He has the ability to manipulate time, move at incredible speeds, and his combat skills are off the charts. Even compared to the most powerful characters in both universes, Whis would be a force to be reckoned with, and his presence would likely change the entire dynamic of the merged universe.
One way could be through a quirk accident. Maybe a character in My Hero Academia has a quirk that can open portals to different universes and accidentally opens one to the Dragon Ball universe. Then, the story can unfold as the characters from both universes interact, learn from each other's powers, and face new threats together.
It's likely Goku. His ability to constantly reach new levels of power like Super Saiyan God and Ultra Instinct is far beyond what most My Hero Academia characters can achieve. Even the strongest in My Hero Academia, like All Might at his prime, would have a hard time against Goku. Goku can destroy planets, while the power in My Hero Academia is more focused on individual combat and saving cities rather than galactic - level threats.
It's a tough call. Goku from Dragon Ball Super has the ability to reach insane power levels like Ultra Instinct. But on the other hand, Acnologia from Fairy Tail is extremely powerful with his dragon - like powers. However, if we consider the potential of Saiyan power growth and Goku's ability to adapt in battle, he might have an edge over Acnologia in a long - drawn fight.
It's likely Goku. His Super Saiyan forms give him incredible power, and his ability to constantly train and get stronger is unrivaled. He could easily defeat most of the Kung Fu Panda characters in a one - on - one fight.
However, All For One could also be a very strong contender. His quirk allows him to steal and use other people's quirks. In a combined universe, he could potentially steal powers from Dragon Ball characters as well. Imagine him with the power of a Saiyan or some of the Dragon Ball energy - based attacks. It would make him an incredibly formidable foe.
It's hard to say, but Goku would be a top contender. His ability to constantly power up and reach new levels of strength like Super Saiyan God and Ultra Instinct is insane. But Ben in his Alien X form from the Omnitrix also has near - omnipotent powers. So it could really go either way depending on how the fanfiction writer sets up the battle conditions.
Friendship is also a big theme. In both Dragon Ball and My Hero Academia, friendship plays a crucial role. Fanfictions will often show characters from both series forming bonds, working together to overcome challenges, and growing as individuals through those relationships.
One interesting crossover could be the characters from My Hero Academia having to face the power levels of Dragon Ball characters. For example, Deku might learn from Goku about the concept of constantly pushing one's limits and training harder. Another could be the quirks in My Hero Academia being combined with the ki abilities of Dragon Ball. Maybe Todoroki's ice and fire quirks could be enhanced with the use of ki control.
If we consider the powers and abilities in both universes in a fanfiction context, I think it could be Eri from My Hero Academia. Her quirk has the potential to be extremely powerful as it can rewind a person's body to a previous state. If she could learn to control it fully, she could potentially 'undo' the powerful undead in the Overlord universe or even reverse the magic spells. However, this is a very speculative idea as she is still a young and inexperienced character, and the power of Ainz Ooal Gown and his allies in the Overlord world should not be underestimated.
Sure. One great 'Dragon Ball My Hero Academia' fanfiction is 'The Quirk of the Saiyan'. It combines the unique powers from Dragon Ball, like Super Saiyan transformations, with the quirk - based world of My Hero Academia in a really interesting way.