One possible storyline could be that Naruto is somehow transported to Goku Black's universe. There, he has to face Goku Black who sees him as an intruder. Naruto would have to quickly learn about Goku Black's powers and find a way to fight back using his ninja skills. Another storyline could be that a powerful villain creates a rift between their two universes and pits them against each other. They start off as enemies but then realize they are being manipulated and team up to fight the real villain.
In a Naruto vs Goku Black fanfiction, a really interesting storyline could be that there's a tournament across different universes. Naruto and Goku Black are both selected to participate. At first, they are just focused on winning the tournament for their own reasons. But as they face each other in the arena, they discover that there's a deeper mystery behind the tournament. It could be that someone is using the tournament to gather energy from their battles. They then have to decide whether to continue fighting each other or team up to stop the real threat. Another possible storyline is that Goku Black's dark energy starts seeping into Naruto's world, corrupting the chakra. Naruto has to fight Goku Black to stop the corruption and save his world.
There could be a storyline where Beerus, out of boredom, decides to train Goku Black instead of fighting him. But Goku Black misinterprets this as a sign of weakness and attacks Beerus. This could lead to a battle where Beerus has to hold back at first to avoid killing Goku Black, but as the fight progresses, he realizes he has to use his full power to subdue him.
One possible storyline could be that Goku Black arrives on Earth in search of a powerful energy source. The Justice League detects his arrival and confronts him. At first, they underestimate his power. Goku Black easily defeats some of the members, but then the League starts to work together and figure out his weaknesses. Another storyline could be that an evil entity has brought Goku Black to the DC Universe to cause chaos and the Justice League has to stop him while also dealing with the entity. Or perhaps Goku Black is tricked into thinking the Justice League are enemies of the Saiyans and he attacks them, only to later find out the truth and have to team up with them to fight a greater threat.
One possible storyline could be that Goku is accidentally transported to Alucard's world. They start off as enemies but then gradually learn about each other's powers and come to respect one another. Another could be that a powerful villain manipulates them into fighting each other. In this case, they might realize they are being used and team up against the real enemy.
One possible storyline could be Goku Black's arrival in the RWBY universe causing chaos as his power level far exceeds that of most characters initially. He might target the powerful relics in the RWBY world, believing they could further his own dark ambitions.
In a fanfiction battle, perhaps the fight begins with Naruto trying to talk to Goku first, to understand his intentions. Goku, not really understanding Naruto's world, just wants to test his strength. So he attacks without warning. Naruto quickly enters his Nine - Tails Chakra Mode to defend himself. The fight then escalates as Goku powers up further. The two exchange blows, with Goku's punches creating shockwaves and Naruto's attacks leaving marks on the ground. As the fight goes on, they both start to respect each other's power and skills, and it becomes more of a battle of wits as well as strength.
In 'Goku betrayed fanfiction', a common plot might be the corruption of his power. Let's say Goku discovers a new form of power that is seen as too dangerous by others. His friends and even some of the Z - fighters fear that he'll lose control and turn on them. So they decide to betray him first to protect the Earth. Another aspect could be a political betrayal. If there were some sort of intergalactic politics involved, Goku might be sacrificed or betrayed by his own side to make a deal with a more powerful alien race. And then there's the idea of a time - travel - related betrayal. Maybe someone from the future comes back and convinces everyone that Goku will cause a great disaster in the future, causing them to betray him in the present.
Perhaps there is a powerful artifact that both Spiderman and the Avengers are after. They end up in a conflict over it. Spiderman, with his street - smart ways, tries to outwit the Avengers and get the artifact for himself, believing he can use it for good in his own way.
A storyline could involve Nightwing being framed for a crime in Gotham. Batman, believing the evidence at first, tries to bring him in. Nightwing, of course, resists as he is innocent, and this leads to their fight. As the story progresses, they both realize there's a bigger conspiracy at play.
One possible storyline could be that Thanos arrives on Earth seeking a powerful artifact. Superman steps in to stop him. They battle it out across the city, with Superman using his strength and speed to try and take down Thanos. Another could be that Thanos somehow manages to get Superman under his control using the Infinity Stones, and then the rest of the Justice League has to figure out how to free Superman and defeat Thanos.
One possible storyline could be a friendship - based plot. Goku, with his pure heart and love for fighting strong opponents, might see 18 as an interesting sparring partner. They could start training together, leading to humorous exchanges as Goku's simple - mindedness clashes with 18's more stoic personality. Another could be a story where they team up to face a new and powerful enemy threatening the Earth. 18's android abilities combined with Goku's Saiyan power would make for an epic battle combination. There could also be a more emotional storyline where Goku helps 18 come to terms with her identity as an android in a world that often views her with suspicion.