They might be very skeptical at first. After all, Percy's powers are based on Greek mythology which is quite different from their world.
The Avengers would likely have a mixed reaction. Iron Man might be intrigued by Percy's abilities and see him as an interesting new element to study. Captain America, on the other hand, would probably be more cautious, not fully trusting this new arrival with his strange powers. Thor, having some knowledge of gods, might be more open - minded and want to learn more about Percy's connection to the Greek gods. Black Widow would be sizing him up, trying to figure out if he was a threat or an ally. Hulk might not care much at first, until Percy did something that either impressed or angered him. Overall, their reactions would depend on how Percy presented himself and what kind of situation they were in when they met.
Some of them might be entertained. For example, Thor could see the similarities and differences between his world and Percy's world of gods and monsters and find it humorous. Others like Black Widow might analyze the characters' motives and strategies in the fanfic as she is used to understanding people's minds.
Percy would probably be very confused at first. He's used to dealing with threats from the world of Greek mythology, not superheroes like the Avengers. But once he realizes he's been kidnapped, he'd likely be angry. He'd try to find a way to escape using his powers, like controlling water to create distractions or even using it to overpower his captors.
Thor would be the most likely to relate to her on some level, as he comes from a world of gods and magic too. He might see her as an equal in a way. Bruce Banner would be interested in the scientific aspect of how her powers work, if there is any scientific explanation within the context of the fanfiction. And the others like Clint Barton and Wanda Maximoff would be curious about her background and how she ended up in their world.
Bruce Banner, when he's not in Hulk mode, would be really interested in the scientific aspects that might be hidden in the Percy Jackson fanfiction. Even though it's a world of magic, he could look for ways that the magic could be related to some kind of scientific principle. He might also be interested in how the characters control their powers, whether it's Percy with his water powers or the Avengers with their various abilities, and look for similarities in self - control and management of power.
Percy's reaction would be complex. On one hand, he would respect the Avengers' powers. He'd see Iron Man's intelligence - based powers as a different kind of 'gift' compared to his own demigod abilities. He might be a bit intimidated by the combined might of the Avengers at first. But then, he would start to analyze their powers. He would think about how Captain America's leadership and physical abilities are like the qualities of some of the heroes in his own world. And he'd be constantly comparing and contrasting their powers with his own and those of his friends, trying to find common ground or new ideas that could help him in his own adventures.
Percy would be angry. He has been through a lot in his own world and being betrayed again would not sit well. He'd probably lash out with his powers at first.
Percy would probably be very angry. He's used to being a hero, not a captive. He might immediately start trying to break free, using his water powers to create distractions or even attack if he feels really threatened.
The Avengers' reactions would be diverse. Tony might be dismissive at first, thinking it's just some kids' stuff. But then he'd get curious and start asking Thor more about the magic and powers in the Percy Jackson universe. Steve would probably listen attentively, seeing it as a new form of hero story. Thor himself would be enthusiastic, trying to get everyone as excited as he is about it.
In a fanfiction, the Avengers' reactions to Percy Jackson's powers would be complex. Natasha Romanoff would immediately start thinking about how to use Percy's powers to their advantage in a mission. Bruce Banner, as the Hulk, might be a bit envious that Percy has such a natural and controlled power, while his own transformation is more of a chaotic force. Steve Rogers would be in awe of Percy's connection to an ancient power source, the Greek gods. And Clint Barton would probably make some jokes about Percy being like a human water hose, but deep down he'd be impressed. Tony Stark would want to incorporate Percy's power - controlling abilities into some new technology, or at least try to understand the science behind it.
Some of the Avengers might be hostile at first. They're used to dealing with threats and Percy, being an unknown with strange powers, could be seen as a danger. But others, like Captain America, might be more open - minded and willing to give him a chance. Stark would probably be very curious about Percy's powers and how they work, and might even try to find a scientific explanation for them.