Dragon Ball Z established the concept of fusion, with the two most famous fusion methods being the Fusion Dance and the Potara earrings.
First, the Fusion Dance in Dragon Ball is a technique Goku learned from the planet Metamor in another world, where it is called Metamorans. It is a technique that fuses two people to create another stronger individual using a characteristic symmetrical pose and requires the two people to be of equal strength.
Second, using the Potara earrings is a fast, powerful, and easy way to fuse, the only requirement is to have a pair of Kaioshin earrings. Using the Potara earrings, anyone can fuse, without requiring a balance of power.
Among the powerful fusion warriors, the Majin Buu Saga almost introduced a fusion warrior stronger than Vegito (the fusion warrior between Goku and Vegeta using the Potara earring). That is the fusion between Gohan and Goku.
During the Majin Buu saga, Goku returned to Earth with Kaioshin's Potara earrings to aid Gohan against Super Buu, after the villain had absorbed Piccolo and Gotenks. Goku's idea was to fuse with Gohan, but it didn't work out. A small mistake completely scrapped the idea, leaving fans wondering how powerful Goku's fusion with his son would be?
The Power of Fusion Between Goku and Gohan in Dragon Ball
In the final story arc of Dragon Ball Z, Goku and Gohan are the two strongest Saiyans, so their fusion would be the strongest. At this point, Gohan has reached the “Mystic” state by unleashing his hidden power, making him as strong as the Super Saiyan 3 level, which can easily surpass Super Buu. This puts Gohan far above Vegeta's level.
Goku with Super Saiyan 2 was able to fight Vegeta at Super Saiyan 2 on par, but Vegeta had the advantage of Babidi's magic, while Goku held his own throughout the fight. Goku and Gohan were very close in level, and this remains true to this day. Since Goku with Ultra Instinct proved to be a worthy opponent for Beast Gohan, this would result in a more balanced and powerful fusion than Vegito.
Furthermore, since Goku and Gohan share techniques, such as the Kamehameha, compatibility would also be better. The father-son duo could also combine their moves and form new abilities, as Vegito demonstrated with the Final Kamehameha.
Goku and Gohan can also use more unique transformations with their fusion. Gohan has the unique Mystic and Beast forms, while Goku has Super Saiyan 3. With Gotenks being able to go SSJ3, it makes sense that the fusion between Goku and Gohan could unlock some new forms.
In the end, there's no doubt that the fusion between Goku and Gohan would be much stronger than Vegito.
