One common theme is power struggles. Since Black Goku is a very powerful character, when he crosses over, there are often battles to determine who is the strongest in the new combined universe.
Vegeta would be a great choice. Their rivalry in the original Dragon Ball series could be taken to a whole new level in a crossover setting. Another good character could be Trunks. Since Goku Black has a connection to Trunks in the main story, it would be interesting to see how they interact in a different scenario.
One idea could be Goku Black crossing over into a modern-day Earth where he has to deal with advanced technology that he doesn't understand at first. Another could be a crossover with a different anime universe, like Naruto, where Goku Black's power clashes with the ninja abilities. Maybe he teams up with Naruto against a common enemy.
One possible scenario could be Goku Black using his power to take over a part of the One Piece world. He might try to find the One Piece itself, thinking it could grant him even more power. His dark nature would likely put him at odds with the Straw Hat crew, leading to epic battles.
A plot could involve Goku Black arriving in the Naruto world during a time of great unrest, like when the Akatsuki is causing chaos. He sees the shinobi as weaklings compared to his Saiyan strength. However, Naruto, with his Sage Mode and Nine - Tails chakra, manages to hold his ground against Goku Black in a first encounter. This catches Goku Black's attention, and he decides to study these 'new' powers. Meanwhile, the shinobi villages must decide whether to see Goku Black as a potential threat or an opportunity to learn from his power. Eventually, they could team up to fight a greater evil that emerges due to Goku Black's presence in their world.
Sure. One interesting 'black goku crossover fanfiction' could be where Black Goku crosses over with the Dragon Ball Z universe in a different timeline. It might explore how his actions change the already complex storylines and power dynamics among the Z - fighters.
In a Goku Black crossover Naruto fanfiction, power levels are a bit tricky to compare. Goku Black comes from a universe where power is measured in ki and he has access to super - saiyan forms which boost his already great strength. Naruto has his own unique power system based on chakra. Initially, Goku Black would seem more powerful as his attacks are more destructive on a large scale. But Naruto has an advantage in his ability to adapt and his connection with the Nine - Tails. Also, Naruto's friends and the entire shinobi world could potentially back him up. So, while Goku Black may start as the more powerful one, in the long run, Naruto's growth potential and the support of his world could make him a strong contender for the most powerful character in this crossover.
The power dynamics. Goku Black is extremely powerful. So in a crossover fanfic, seeing how he measures up against other powerful characters from different franchises is exciting. Like in a crossover with the One Piece world, his ki blasts against the Devil Fruit users' powers make for great battles.
One interesting fanfiction could be about Goku and Black Goku teaming up against an even greater threat from another universe. In this story, they might initially be at odds but gradually learn to work together, using their unique abilities to save the multiverse.
In fanfiction about Goku and Goku Black, a common concept is the alteration of their power levels. Writers may give Goku new forms or boost Goku Black's abilities in unexpected ways. There can be stories centered around Goku Black's adaptation to the main timeline's culture and society. For example, he might have to deal with the everyday life in addition to his evil plans. And there are fanfictions that focus on the psychological impact of their battles on each other, like how Goku might be affected by constantly facing an evil version of himself.