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.
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.
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 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.
Well, Vegeta could also be a contender for the strongest in this crossover. He has his own set of powerful transformations. However, if we consider the more mystical aspects of Naruto, like the power of the Rinnegan, characters like Sasuke could also be very strong. In a crossover, if Sasuke were to combine his Sharingan and Rinnegan powers with some of the ki - based techniques from Dragon Ball Z, he could be extremely powerful. It really depends on how the writer wants to balance the different power systems.
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.
One interesting crossover could be the fusion of power-ups. For example, Deku with the power of Super Saiyan. He could combine his One For All with the raw strength and speed of a Super Saiyan, making him an even more formidable hero. It would be amazing to see how he controls this new power and how it affects his relationships with his classmates.
It's really hard to say. Goku in his Super Saiyan Blue form has incredible power and can destroy planets. But Naruto in his Six Paths Sage Mode also has amazing abilities. However, if we consider raw power, Goku might be more powerful as he can reach levels of power that can destroy entire solar systems. But Naruto's intelligence and his ability to strategize could give him an edge in a fight.
It's hard to determine a single strongest character as it depends on various factors. Deku has great potential with One For All and Shigaraki has become a major threat with his evolving powers.