A Goku and Goku Black fusion in fanfiction could be really exciting. The fusion would inherit Goku's love for fighting and getting stronger, but also Goku Black's ambition. Their combined ki could be a new type of energy that no one has ever seen before. This new fused form might also have new transformations or abilities. For example, it could combine Goku's Super Saiyan forms with Goku Black's Rose form in unexpected ways. It could change the power balance in the Dragon Ball world and open up all sorts of new storylines, like teaming up with other characters to take on new threats or even having internal struggles between the two personalities within the fusion.
It could be insanely powerful. Goku already has incredible power levels, and Goku Black is no slouch either. When they fuse, it's like combining two nuclear reactors. Their power could be so great that they could effortlessly destroy planets just by flexing their newfound power. They might be able to reach Super Saiyan forms that are far beyond what we've seen in the official series, with power levels that are basically off the scale.
I think Zeno would be a really tough opponent. Zeno has the power to erase entire universes, and a Goku and Goku Black fusion, despite being extremely powerful, would have a hard time against such a being with god - like powers.
In fanfiction, a Naruto and Goku fusion could be extremely powerful. They both have unique abilities. Naruto has his ninja skills like shadow clones and Rasengan, while Goku has his Super Saiyan forms and Kamehameha. The fusion might combine Naruto's strategic thinking as a ninja with Goku's straightforward combat style. It could result in a character who can quickly assess a situation like Naruto and then attack with overwhelming power like Goku.
In a Naruto - Goku fusion, there could be a new form of energy manipulation. Goku manipulates ki, and Naruto uses chakra. They might create a hybrid energy that has the best of both worlds. This energy could be used for long - range attacks like Goku's energy blasts and also for close - combat like Naruto's Rasengan. Also, the fusion could have enhanced senses, borrowing from Goku's Saiyan senses and Naruto's ninja training.
Well, it could be super powerful. The fusion might have Goku's Saiyan strength and ability to transform into Super Saiyan forms, combined with Naruto's ninja skills and chakra control. It could fly around with the speed of a Saiyan and use Rasengan - like attacks with the power of a Kamehameha. Just imagine a character with the orange gi and a headband.
In a Naruto - Goku fusion fanfic, the power - ups could be really exciting. Since Goku has his Zenkai boosts, and Naruto can gain more chakra and power as he progresses in his ninja journey, the fusion might have a new type of growth system. For instance, every time the fusion is in a tough battle, it could gain a permanent boost in strength, speed, and energy. Also, the fusion could potentially access a new form that combines the Super Saiyan transformation and the Nine - Tails' chakra mode for an insanely powerful state.
It could be amazing. Picture Naruto's ninjutsu combined with Goku's ki attacks. They might create new super powerful moves. For example, Naruto could use his shadow clones to multiply Goku's Kamehameha, making it an unstoppable force. Also, their personalities would blend, with Naruto's determination and Goku's love for a good fight.
It could be someone like Frieza. Frieza is extremely powerful and evil in the Dragon Ball universe. If he somehow found his way into the Naruto universe or if the fusion character was in the Dragon Ball universe, he would be a great threat. His ability to transform and his cold - blooded nature would make him a tough opponent for the fusion of Goku and Naruto.