In a Naruto and Spiderman fanfiction, it could be that there is a new threat that is a combination of the powers from both universes. For example, a villain who can create shadow clones like Naruto and also has the super strength and agility of Spiderman. Naruto and Spiderman would need to figure out each other's strengths and weaknesses quickly in order to defeat this powerful foe.
Well, perhaps in the fanfiction, Spiderman gets transported to the Naruto universe. He has to learn how to use chakra and ninjutsu with Naruto as his teacher. They could go on missions together and Spiderman's web - slinging abilities could be combined with Naruto's Rasengan for some really cool combat moves against common enemies in the Naruto world.
One idea could be that Naruto gets bitten by a radioactive spider instead of Peter Parker. So he has to balance his ninja training with his newfound spider - like abilities. He might use his chakra to enhance his spider - sense or web - slinging skills.
One idea could be that Spiderman and Rogue team up to stop a powerful villain who has the ability to control minds in a big city. Rogue's power to absorb abilities could come in handy when they face tough opponents. For example, she could absorb the strength of a super - strong henchman and use it to fight back.
One idea could be that Spiderman 2099 has to team up with a group of rebels from a future dystopia to take down a powerful corporation that controls the city. They might face advanced technology and dangerous enforcers.
One idea could be that Spider - Man gets transported to the world of Frozen. He could use his web - slinging abilities to traverse the icy landscapes. Maybe he helps Elsa control her powers better by showing her how to focus her energy, like he does when he's swinging through New York.
One idea could be a Spiderman and Iron Man crossover. Picture Spiderman getting some high - tech upgrades from Stark. Another is a crossover with the X - Men. Spiderman could interact with mutants and learn new ways to use his powers. Maybe he teams up with Wolverine for a street - level mission.
Another idea is a time - travel fanfiction. Spider - Man could be sent back in time to when his Uncle Ben was still alive. He would have the chance to prevent his uncle's death, but he'd also have to deal with the consequences of changing the timeline, like how it might affect his own development as a hero.
A story could be set in a future where the worlds of Marvel and DC have merged. Spiderman and Starfire are part of a new superhero team. They have to deal with the cultural differences between their two groups of heroes as well as face off against new villains created by the merger of the two universes.
One idea could be exploring what would happen if Spider - Man had to team up with a villain to stop a greater threat. For example, partnering with Doctor Octopus to take on an alien invasion.
One idea could be exploring Spiderman's inner struggle with his dark urges while facing a new and extremely powerful villain. He might have to constantly battle his darker side to not let it take over as he tries to protect the city.
A cool fanfiction concept could be that Spider - Man gets some ghost - like powers temporarily. Danny Phantom has to train him to control these new powers. They could start off not getting along very well because they have different ways of doing things. Spider - Man is used to his high - tech gadgets and relying on his physical abilities, while Danny is more about using his ghostly abilities. But as they train together, they learn from each other and form a strong friendship. And in the end, they use their combined skills to defeat a powerful enemy that neither could have defeated alone.