Maybe the Vulture. He's always on the lookout for new tech to sell on the black market. When he hears about Ant Man's unique shrinking abilities, he decides to capture Ant Man and force him to reveal his secrets. Spider Man steps in to protect Ant Man, and they have to fight the Vulture together.
Perhaps in the fanfic, Ant Man accidentally shrinks himself too much and gets lost in Spider Man's suit. Spider Man then has to figure out how to get him out without harming him. Meanwhile, they discover that there's a mini - world inside the suit with its own set of problems, like tiny villains causing chaos, and they have to deal with that together.
One possible villain could be Doctor Octopus. He might be back with some new and improved mechanical arms, and he wants to prove that he's the superior scientist and villain by defeating both Spider Man and Spider Girl.
Well, it could be about them teaming up to fight a new supervillain in the city. Maybe they start off not getting along because they have different fighting styles, but then they learn from each other and become great partners.
One interesting fanfiction could be where Ant - Man and Spider - Man team up to stop a villain who can manipulate time. In this story, Spider - Man's agility and Ant - Man's ability to shrink and grow would create some really cool action scenes.
Another option is to check out Tumblr. There are often fanfiction writers who post their work there, especially short stories or snippets. You can follow relevant tags such as '#Ant - Man #Spider - Man #fanfiction' to discover new and interesting stories. Plus, Tumblr often has a community aspect where fans can discuss the fanfiction they've read and recommend good ones to each other.
One great 'Ant Man Fanfic' is 'The Adventures of Ant Man in the Quantum Realm'. It really dives deep into the unique world of the Quantum Realm that we saw in the movies. It has exciting action scenes where Ant Man uses his shrinking and growing abilities in creative ways to overcome villains.
Well, it could be about Ant Man bringing his unique shrinking abilities to help the Avengers in a new, unexpected threat. Maybe he shrinks down to infiltrate an enemy's base that the Avengers can't access otherwise.
It could be his mentor. In the fanfic, the mentor might think that Spider Man is becoming too powerful and is a threat to the balance of power. So, he could betray Spider Man by leaking his secret identity or setting him up to be captured by the authorities.
A good 'Ant Man Fanfic' should have a solid understanding of the source material. For example, it needs to accurately portray Ant Man's powers like his ability to shrink and communicate with ants. If it gets these basic things wrong, it can be really off - putting.