To develop their relationship in fanfiction, one approach could be to give The Vulture a more sympathetic backstory. Maybe he was wronged by the city's elite and turned to crime as a way to get revenge. Spiderman, upon learning this, starts to see him in a different light. They could then have a series of interactions where Spiderman tries to persuade The Vulture to use his skills for good. Also, if there was an event that put someone they both care about in danger, like a civilian or a family member, they would have to cooperate to save that person, which would deepen their connection.
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.
There were two actors playing Vulture, Sun Xun and Michael Keaton. Sun Xun played the role of Vulture in the TV series I Am Special Forces, while Michael Keaton played Vulture in the movie Spider-Man: Heroes Return.
A great way to write a compelling Vulture in fanfiction is to base his actions on his backstory. If he was once a bullied or overlooked individual, his actions as Vulture could be a way to prove himself. His dialogue should be sharp and to the point, showing his intelligence. When he interacts with Spider - Man, don't just make it a one - sided battle. Have them exchange taunts and threats that reveal more about both characters. And don't forget to make his appearance unique. His vulture - like features should be more than just for show; they should be part of his identity and how he approaches combat.