Thor might accidentally start a conflict at first. His brash and confident nature could be misinterpreted by Percy and his friends. For example, if Thor makes a grand entrance and shows off his power, Percy's group might think he's being aggressive. This misunderstanding could lead to a brief moment of tension or even a small scuffle before they realize they're on the same side.
It could also be Ares, from Percy Jackson's side. Ares is the god of war and is often looking for a fight. When he sees the powerful Avengers, he might be eager to test his strength against them. He may not care about the potential consequences and just jump into a conflict, dragging others along with him whether they like it or not.
Loki could be the one most likely to start a conflict. He's always been a bit of a troublemaker in the Avengers world. In a meeting with Percy Jackson and his group, Loki might see an opportunity to cause chaos. He could try to manipulate the situation by pitting the Avengers against Percy and his friends, thinking he can use the confusion to his advantage.
I think Percy and Thor would be an interesting pairing. Thor is a god from Norse mythology and Percy is a demigod from Greek mythology. They could compare their powers and stories about their respective gods. Thor's hammer and Percy's sword could be used in some cool battle scenes together.
Thanos could still be a likely villain. Even if he was defeated in the official storyline, in a fanfic he could return more powerful or with a new plan. His obsession with the Infinity Stones makes him a great overarching threat.
I think Iron Man and the Flash would get along well. Iron Man is always interested in new technology and the Flash's super - speed abilities are like a form of amazing technology. They could have long discussions about how the Flash's powers work and Iron Man might even try to create something inspired by it.
It could also be Annabeth and Black Widow. Both are highly intelligent and strategic. Annabeth's knowledge of architecture and ancient languages might be useful to Black Widow in certain situations, like deciphering an ancient code related to a new threat. Black Widow, in turn, could teach Annabeth some self - defense and espionage skills. They would see the value in each other's abilities and form an alliance quickly.
Hawkeye might be one. He's always on high alert and if he senses any threat from Team Red, he could be the first to draw his bow. He's very protective of his team and the world, so any sign of trouble from a new group could set him off.
Batman and Iron Man could potentially have a conflict. Both are brilliant, wealthy, and used to being in control. They might clash over strategies or leadership within a joint mission. Iron Man with his high - tech suit and more flamboyant style might not immediately see eye - eye with Batman's more brooding and stealthy approach.
Iron Man and Batman might be the most likely to clash. Iron Man is all about high - tech and showing off his latest inventions. Batman, while also using technology, is more of a brooding, solitary figure. Iron Man might see Batman as a bit of a relic or too old - fashioned in his methods. Batman, in turn, could view Iron Man as a bit too flashy and irresponsible with his power. Their egos could get in the way of them working together initially.
Another interesting interaction would be between Annabeth and Tony Stark. Annabeth is highly intelligent and strategic, much like Tony. They could either be in a battle of wits, constantly trying to one - up each other in terms of coming up with plans, or they could end up working together really well. Annabeth could teach Tony about ancient Greek architecture and strategy, while Tony could show her some of his latest high - tech inventions.
Annihilus could be a likely villain. He is a powerful being from the Negative Zone. In the fanfiction, Annihilus could be drawn to Earth because of the energy signature created when the Avengers and Captain Marvel meet. He sees Earth as a prime target for conquest. His powerful cosmic control rod gives him an edge in battle. The Avengers and Captain Marvel have to quickly learn about his weaknesses and use their combined powers to stop him from destroying Earth and spreading his reign of terror across the universe.
Percy Jackson and Thor would be an interesting pairing. Percy has his water powers and connection to the sea, while Thor has his lightning powers. They could have some really cool battle scenes together, like when they face a water - and lightning - based enemy. Also, they both have a bit of a sense of humor and a heroic nature, so they'd probably get along well.