A possible storyline is that a mutual enemy frames them for crimes they didn't commit. They are forced to work together to clear their names. Spiderman uses his detective skills to find clues and Shadow uses his stealth to gather information. As they dig deeper, they discover a conspiracy that is much larger than they initially thought, and they have to put aside their differences to stop it.
One potential storyline could be a race against time. A powerful alien artifact has landed in their city and both Spiderman and Shadow want to get to it first. Spiderman wants to keep it safe from falling into the wrong hands, while Shadow believes it could be the key to achieving his own goals. Along the way, they face various obstacles and start to respect each other's abilities.
One common storyline is them facing an alternate - dimension threat. Since they both come from different versions of the Spider - Verse, there could be a menace that is messing with the fabric of their universes, and they have to work together to stop it.
A potential storyline could be a joint mission. The Citadel Council and the UNSC team up to face a common threat, like a new powerful alien race. During the mission, they learn to understand and respect each other's capabilities.
In a 'Naruto meets Konan' fanfiction, there could be a time - travel plot. Naruto somehow gets sent back in time and meets a younger Konan. He tries to prevent some of the tragedies that happened in her life, like the death of Yahiko. This changes the future and creates a whole new dynamic between Konoha and Amegakure.
A potential storyline could be that Gine saves Goku from a powerful enemy. Since she is his mother, she has a strong instinct to protect him. Another could be that Goku and Gine team up to fight against Frieza or other villains who pose a threat to the universe.
Well, in this fanfiction, Spiderman might learn some new skills from the Shadow. The Shadow could have some unique fighting techniques or ways of moving around the city that Spiderman has never seen before. So, Spiderman could incorporate those into his own fighting style. Also, their personalities could clash at first. Spiderman is more of a talkative and quippy hero, while the Shadow is often more brooding and mysterious. But eventually, they could find common ground and work together really well.
In such a fanfiction, Spiderman and Shadow might initially be at odds. Spiderman, with his sense of justice and responsibility, could view Shadow as a threat due to his more brooding and sometimes violent nature. However, they might find common ground in fighting a greater evil. For example, a powerful villain that neither could defeat alone. They could combine their unique abilities, Spiderman's web - slinging and superhuman strength with Shadow's speed and chaos powers to take down the bad guy.
A potential storyline could be Nightwing joining the Justice League on a trial basis. He has to prove himself to the more established members. This could involve a series of missions where he showcases his skills in detective work, combat, and teamwork. Another storyline could be Nightwing being wrongly accused of something by the Justice League, and he has to clear his name while also dealing with the threat of a common enemy.
Perhaps the Green Goblin could be the villain. He's a classic Spiderman foe and could pose a real threat to both Spiderman and the Shadow.
Another storyline could involve Nico being on a quest in his own world, but it somehow intersects with Gotham. For instance, a powerful magical item has been stolen and ends up in Gotham. Nico follows it there and meets Batman. At first, they don't see eye to eye as they have different methods. But as they face challenges together, such as fighting off the villains who also want the item, they start to understand and trust each other more. This could lead to a long - term friendship or at least an alliance where they help each other out in future situations.
One storyline could be that they are brought together by a time - traveling device. Maybe an enemy is using time travel to change history and they have to stop it. Spider - Man, Bucky, and Steven are all from different eras or backgrounds, so they would have to work together to figure out how to fix the timeline.