One idea could be Venom bonding with Hulk. Imagine the power boost and the chaos they could cause together. Another is Venom facing off against Thor. The contrast between Thor's godly powers and Venom's alien abilities would make for an exciting battle. Also, Venom could team up with Black Widow and use his stealth and her combat skills for some undercover missions.
In an 'Avengers Venom crossover fanfiction', perhaps Venom's host could be a new character related to one of the Avengers. For example, the son of Captain America who somehow gets bonded with Venom. This would create a whole new dynamic within the Avengers. The team would be conflicted between their loyalty to Cap and their fear of Venom. Meanwhile, Venom would have to learn to co - exist with the Avengers' values and not just go on a rampage.
One idea could be a Venom crossover with Spider - Man in an alternate universe where they have to team up against a common enemy like Carnage. Another could be a Venom and Deadpool crossover, with their crazy personalities clashing and then somehow working together. Maybe a Venom crossover with the X - Men, where Venom's alien nature causes some interesting reactions among the mutants.
I think Spider - Man would be really interesting. Since in the comics, Venom has a long history with Spider - Man, and if you bring that into the Avengers' world, it could add a whole new layer of drama. The Avengers would be caught in the middle of their relationship, not fully understanding the complex history between them.
Another interesting concept is an OC who is a scientist researching Venom's origin. They accidentally get infected and use their new powers to help the Avengers in a unique way. For example, they could have enhanced senses that allow them to detect threats before the Avengers even know they're there. They also have to struggle with the dark side of the Venom symbiote while trying to be a hero.
Perhaps Venom could cross over with the Guardians of the Galaxy. Venom's dark and edgy nature would contrast well with the Guardians' more light - hearted and space - faring adventures. They could be forced to work together to stop a powerful alien threat that is drawn to Venom's symbiote powers.
One common theme is the clash of ideologies. Venom has a more chaotic and anti - hero approach compared to the Avengers' heroic and morally upright stance. Another theme is redemption. Sometimes Venom is on a path to redeem himself through his interactions with the Avengers.
One possible storyline could be Venom getting involved in an Avengers mission. Maybe Venom's unique abilities like his symbiotic powers and super strength could be used to help the Avengers against a common enemy. For example, against a powerful alien threat that the Avengers alone can't handle. Venom's ability to blend into the shadows and his near - indestructibility could give the Avengers an edge in battle.
Another interesting plot could be that a mad scientist creates a device that can separate Venom from his host. However, the separation goes wrong and the symbiote energy starts to spread across the city, infecting people. Spider - Man and Venom must work together to find a way to contain the energy and save the city.
Well, a cool Venom and Spider - Man crossover fanfiction idea might be that there's a strange alien invasion. But this time, the symbiotes are being controlled by an even greater evil. Venom, having his own sense of justice, decides to work with Spider - Man. They start off not trusting each other much, but as they face the challenges, they learn to rely on one another. Also, perhaps Spider - Man has to deal with some of Venom's more violent tendencies during the fight.
One idea could be that the Avengers get transported to a Disney fairy - tale world. For example, they end up in Arendelle from 'Frozen'. Iron Man could try to figure out how to adapt his suit to the cold, while Captain America tries to lead the way through the icy terrain. Thor might find similarities between the magic in Arendelle and Asgardian magic.
Another concept could be that one of the NCIS agents has a family member who is in danger because of a supervillain's plot. The Avengers get involved to protect the agent's family, but the NCIS team doesn't trust them at first. Gibbs would be very protective and suspicious. As the story progresses, they all learn to work together. Ziva could show off her combat skills to Black Widow, and they could have a friendly sparring match while sharing their combat experiences.