Here's a story idea. There's a new power source that both Thanos and Spiderman are after. Thanos wants it to increase his power for his grand plan, while Spiderman wants to keep it out of Thanos' hands. Along the way, they get trapped in an alternate dimension together. In this dimension, they have to work together to survive and escape. During this time, they learn more about each other's motives and there's a slow - building respect between them, even though they are still on opposite sides once they get back to their own world.
A unique story idea could be a time - travel fanfiction. Spiderman travels back in time to before Thanos starts his quest for the Infinity Stones. He tries to prevent Thanos from ever becoming the threat he is. Or, what if there was a reality where Thanos was a hero and Spiderman was the villain? Explore how their roles are reversed and how they interact in this new dynamic. It would be really interesting to see how their personalities change according to their new alignments.
One idea could be that Thanos, for some strange reason, decides to take Spiderman under his wing. Maybe he sees potential in Spiderman and wants to use him for his own purposes. But Spiderman resists and tries to turn Thanos from his evil ways. Another idea is that a spell gone wrong by a sorcerer combines Thanos and Spiderman into one being, and they have to figure out how to separate while dealing with the chaos that ensues.
First, think about the conflict. Since Thanos is a powerful villain and Spiderman is a street - level hero, you could have Thanos target something in Spiderman's neighborhood, like a powerful artifact. Then, for character development, show how Spiderman struggles with his own insecurities in the face of such a powerful foe. He might question if he's really able to make a difference. You can also add some interesting twists. Maybe Thanos has some unexpected respect for Spiderman's tenacity.
One idea could be a story where Spiderman has to team up with his greatest enemies to fight a new, more powerful threat from outer space. This would force him to put aside his differences and find common ground with the likes of Doctor Octopus and Green Goblin.
One idea could be that the OC is a scientist who accidentally creates a device that can disrupt Spiderman's powers. This leads to a series of events where they have to work together to fix it while also facing off against a new villain who wants to use the device for evil. Another could be the OC is a new superhero in training and Spiderman becomes their mentor, and they develop a close bond as they fight crime together.
One plot idea could be that Spiderman gets transported into the Overwatch universe. He has to team up with the Overwatch heroes to stop a villain who has technology that can disrupt both universes. For example, Doomfist might be interested in using this technology to gain more power, and Spiderman's agility and unique powers would be useful in the fight.
One idea could be that The Vulture has a change of heart after Spiderman saves his life in a dangerous situation. He then decides to use his knowledge of technology to help Spiderman secretly against other villains. Another could be a story where they are forced to team up in an alternate dimension where they are the only ones who can stop a greater threat. A third idea is that The Vulture's daughter is in danger and Spiderman has to help him save her, which then leads to a strange alliance between them.
In a Venom x Spiderman fanfiction, a plot could involve Venom and Spiderman having to work together to stop a symbiote invasion from another dimension. The symbiotes from this other dimension are more aggressive and have different abilities. Spiderman has to use his intelligence and web - slinging skills, while Venom uses his brute strength and symbiotic powers. Along the way, they could start to understand each other better, and Venom could learn some of Spiderman's sense of responsibility. This would be a great opportunity for character development for both of them.
One idea could be that Venom and Spider - Man are forced to team up against a new symbiote villain that is far more powerful and malevolent. This new symbiote could be controlling innocent people, and Spider - Man and Venom have to find a way to stop it without harming the hosts.
One idea could be that they team up to fight a new villain who has the ability to manipulate time. This would put their different powers and personalities to the test as they try to stop the villain before he changes the timeline too much.
One idea could be exploring how the relationship between Spiderman and Venom changes during the pregnancy. Maybe they become more protective of each other.
A plot could involve Spiderman being suicidal due to some big mistake he thinks he made, like accidentally endangering a lot of civilians. Deadpool, with his unorthodox methods, could help Spiderman see that mistakes are a part of being a hero and that he can still make amends. For example, they could team up to take on a villain who is specifically targeting Spiderman because of his vulnerable state, and in the process, Spiderman regains his will to live.