Maybe in the fanfic, Batman's rogues gallery somehow teams up with some of the Avengers' villains. This forces Batman and the Avengers to work together. Batman could introduce his unique gadgets and combat style to the Avengers, while they could show him their superpowers up close. For example, Iron Man could be intrigued by Batman's utility belt and try to create his own version of some of the gadgets.
It could be really exciting. Batman's detective skills and gadgets would add a new dimension to the Avengers. He might outwit some of the Avengers' enemies with his superior intellect. For example, when facing Loki, Batman could use his knowledge of psychology to manipulate Loki's actions. His utility belt with all its cool gadgets like the grappling hook and batarangs would be a great addition to the team's arsenal.
He might fit in as a sort of mentor figure. He has years of experience fighting crime in Gotham. He could teach the younger Avengers like Spider - Man (if he's in the mix) some valuable lessons about perseverance and the importance of a strong moral code. Also, his physical combat skills would be useful in hand - to - hand battles against powerful foes.
One possible plot could be that Batman's Gotham is threatened by a powerful villain who has some connection to the Avengers' universe. Maybe Loki decides to cause chaos in Gotham as part of a larger plan against Earth. Batman, being the detective he is, starts to investigate and soon realizes that this is no ordinary criminal. He then somehow gets in touch with the Avengers, perhaps through SHIELD's intelligence network. Together, they combine their skills and resources to take on Loki and his minions. Batman's stealth and strategic mind would complement the Avengers' superpowers.
Well, it could be really chaotic. The Avengers come from their own universe with superpowers and complex relationships. A Batman fanfic usually has its own dark and gritty tone. If they met within the context of a fanfic, there might be a clash of ideologies. The Avengers might not understand Batman's more brooding and solo nature, while Batman fans might find the Avengers' flashy powers a bit over - the - top. Maybe the Avengers would try to recruit Batman from the fanfic world, thinking his detective skills could be useful.
They could start by trying to understand the different rules of that world. Since Batman's world is more grounded in detective work and street - level crime fighting compared to the Avengers' world of superpowers and global threats. The Avengers might use their powers to help solve some of the complex mysteries in the Batman fanfic world. For example, Vision could use his ability to see through objects to find clues that Batman might miss.
In such a fanfic, there could be a clash of ideologies. Batman is a brooding, solo vigilante with his own set of rules in Gotham. The Avengers, on the other hand, are a team with different powers and personalities. They might initially be suspicious of Batman's methods. But they could also learn from each other. Batman could show them his detective skills and stealth, while the Avengers could introduce him to a wider range of superpowers and team - based strategies.
The plot could start with Batman getting an invitation from SHIELD. They've noticed some strange activities in Gotham that seem related to a threat that could affect the whole world. Batman joins the Avengers. He quickly realizes that their methods are very different from his. But he uses his stealth and detective skills to gather information that the Avengers couldn't. For example, he discovers a hidden base of the villains by following a small clue.
A great plot could involve a time - travel aspect. Batman discovers a device in the Batcave that sends him back in time to the early days of the Avengers. He has to work with a young and inexperienced Avengers team to stop a threat that, if not stopped, will change the future in a bad way. Maybe this threat is an ancient evil that was sealed away but is now being awakened. Or, there could be a plot where Batman's rogues gallery teams up with some of the Avengers' villains. The combined forces of villains create a huge problem, and Batman and the Avengers have to put aside their differences and strategies to take them down. Also, a plot where an alien race is interested in Batman's technology and kidnaps him. The Avengers rescue him, and in return, Batman helps them upgrade their own tech to fight off the alien race's invasion.
In a fanfic, a cosmic entity could be the key. This entity decides to create an experiment and brings Batman to the Avengers' universe. At first, there would be some tension. The Avengers might not trust Batman right away as he is an unknown from another world. But as they see him in action, taking on foes with his martial arts and strategic mind, they start to respect him. Batman, on the other hand, would have to adapt to the more out - there threats that the Avengers usually deal with, like alien invasions and magic - based villains.