Perhaps the Avengers are under some sort of mind - control spell. Spiderman, being immune to the spell for some reason, has to figure out how to break it. He might swing around, avoiding attacks from his brainwashed friends, and then find a way to disrupt the source of the mind - control. For example, he could web up a device that was emitting the mind - controlling waves.
A possible plot twist could be that Spiderman is actually from an alternate dimension where he has different powers. And these powers are the key to saving the Avengers. For example, he might be able to time - travel in this dimension and go back to prevent the event that put the Avengers in danger in the first place.
Well, in this fanfiction, it could be that Spiderman uses his agility and web - slinging skills to outmaneuver the enemy. Maybe he creates a huge web shield to protect the Avengers from a powerful blast. His spider - sense could also alert him to hidden dangers that the Avengers might not notice, allowing him to save them at the crucial moment.
Well, one possible plot could be that during a big battle where the Avengers and Spiderman are fighting side by side against a powerful enemy like Thanos. Spiderman, being young and perhaps a bit over - eager, jumps into a dangerous situation without proper backup. He gets injured while trying to protect an Avenger, say Captain America. This could lead to a lot of guilt among the Avengers for not being able to protect him better and also Spiderman having to deal with his own physical and mental recovery.
Well, it could be about Spiderman teaming up with the three Avengers to fight a new super - villain. Maybe they have to stop a powerful alien from taking over the earth. Spiderman's agility and quick thinking combined with the Avengers' unique powers would make for an exciting story.
The plot could involve Castiel being summoned by a magical accident in the Avengers' universe. He then realizes that there is a great evil approaching, something that not even the combined might of the Avengers can handle. So, he decides to use his knowledge of the supernatural and his powers to help them. He might have to teach the Avengers about the existence of angels and other celestial beings to make them understand the true nature of the threat. Along the way, there could be some really interesting interactions between Castiel and the different Avengers members. For example, his stoic and otherworldly nature could contrast with Tony Stark's sarcastic and scientific mind, leading to some great dialogue.
One interesting plot could be Spider - Man having to prove himself to the Avengers. Maybe he starts as an outsider, but through his unique skills like web - slinging and his spider - sense, he helps the Avengers in a mission that they initially thought was impossible. For example, infiltrating a high - security enemy base that is full of high - tech traps.
The plot could involve the overpowered original character (OC) having some unique ability like super speed and time manipulation. They might first notice the Avengers in a dire situation, say being overwhelmed by an army of powerful villains. The OC could then use their powers to quickly turn the tide. For example, they could freeze time, isolate the villains one by one, and defeat them easily, saving the Avengers in a spectacular fashion.
The three Avengers could be Iron Man, Captain America and Thor. Iron Man could provide the high - tech gadgets and strategic thinking. Captain America would bring leadership and his combat skills. Thor with his godly powers like lightning and super strength would be a great addition. They would each have different interactions with Spiderman, for example, Iron Man might be like a mentor to him, while Thor could be more of a friendly rival in terms of strength.
Well, perhaps in this fanfic, the Avengers misunderstand Spiderman's actions. Maybe they think he's been compromised by some powerful enemy force, so they decide to kidnap him to figure out what's really going on. They could take him to a secret location, like an abandoned SHIELD base. Then Spiderman has to convince them that he's on their side while also dealing with his own feelings of betrayal.
A cool plot could be that a villain creates a device that can manipulate time. This device causes chaos as it starts to merge different timelines. Spider - Man gets caught in the middle of this temporal mess while on a normal patrol in New York. He then reaches out to the Avengers for help. The Avengers, who have experience with time - related issues from previous adventures, team up with Spider - Man. Thor uses his lightning to disrupt the device's power source, while Spider - Man swings in to physically disable it with the help of Black Widow's combat skills. In the end, they manage to restore the timelines and save the day.