Goku Black could be a powerful new threat. His ability to instantaneously move between spaces using his powers would be like a more advanced form of the Shanks' ability to appear suddenly. He could easily target the weak points of the various islands in the One Piece world.
Goku Black might be seen as a sort of otherworldly being in the One Piece universe. He could start by causing chaos on a small island, which would attract the attention of the Straw Hat crew. His powers are so different from Devil Fruits and Haki. He could potentially teach some characters about new forms of combat, or he could just be a pure antagonist, bent on destruction and domination.
Well, Goku's extreme power level could make him a sort of legend in the Naruto fanfiction world. His Saiyan abilities like the Kamehameha and Super Saiyan forms would be completely foreign to the ninjas. He might be seen as an otherworldly being, and his presence could disrupt the power balance. Maybe he'd come to the Naruto world seeking a new challenge, or perhaps he was accidentally transported there.
She'd fit in as a unique addition. Her magical abilities would set her apart. She could use magic to enhance the crew's abilities. For example, give Luffy a temporary boost in strength with a spell.
Well, Goku's super strength and fighting abilities could make him a powerful ally or a formidable foe in the Naruto world. His ki powers might be seen as a strange new form of chakra. He could also teach the Naruto characters some of his unique fighting techniques, like the Kamehameha wave.
Well, in Naruto fanfiction, Goku and Vegeta might be introduced as legendary figures. Goku's kind - hearted and always - ready - to - fight nature could be seen as an inspiration to some of the younger Naruto characters. Vegeta's journey from a villain - like character to a more complex anti - hero in his own story could be mirrored in the Naruto universe. They could be brought in to help during a major crisis, like when the Akatsuki was at its peak, using their unique powers to turn the tide.
Goku would fit in as a super - powerful outsider. His physical strength and combat skills are far beyond what the normal characters in Highschool DxD are used to. He could become a sort of protector for the school, using his powers to fend off any threats that come their way. His energy - sensing ability would give him an edge in detecting hidden enemies.
In fanfiction, Goku Black could be incorporated into the Justice League as a sort of experiment. The League, always looking for ways to increase their power and protect the world, might see his abilities as a valuable asset. However, his different moral code and origin from another universe would create a lot of tension. There could be a story arc where the League tries to reform him or at least control his more violent tendencies while using his power to fight against threats that are beyond their normal capabilities.
Goku would probably be very friendly with Luffy. They both love to fight strong opponents and have a sense of adventure. Goku might be a bit confused by some of the wacky things in the One Piece world like the Devil Fruits at first, but he'd quickly adapt. He'd also likely be impressed by the determination of the other characters like Zoro and Sanji.
Well, Goku Black could be a powerful antagonist in the RWBY fanfic. His combat skills and powers from the Dragon Ball universe would make him a formidable foe. He could have his own motives, like seeking power in the RWBY world or trying to impose his own sense of order. For example, his ability to use ki blasts could be a new and terrifying threat to the Huntsmen and Huntresses in RWBY.
Well, Goku could be a powerful Jedi or Sith in a fanfic. His super strength and fighting skills would make him a force to be reckoned with. He might use his Ki abilities like the Force, and his Saiyan transformations could be seen as a new kind of power-up in the Star Wars world.
She's brave and determined in the Harry Potter world, and those traits would serve her well in One Piece. She'd probably be just as eager to take on challenges and fight for what's right.