Black Widow could also be the main character. Her past with the darker side of things (her time as a spy in Russia) gives her a unique perspective. She could be infiltrating Hydra to find out about the experiment, using her skills to gather intelligence and then work with the other Avengers to take down Hydra and deal with the consequences of the experiment.
Captain America could be the main character. Since he has a long - standing history with Hydra (in the sense of fighting against their evil), he could be the one leading the charge to uncover and stop the Hydra experiment. His strong moral compass would make for an interesting dynamic as he tries to save those affected by the experiment.
Well, a possible plot could be that the Hydra experiment was actually a cover - up for a much larger and more sinister plan. The Avengers discover that the experiment was just the tip of the iceberg and they have to race against time to stop Hydra from unleashing something far worse. It could also be interesting if the experiment somehow gives an ordinary person the ability to see into the future, and that person becomes a key figure in the battle between the Avengers and Hydra.
Definitely the Avengers members like Captain America, Iron Man, Thor, Hulk etc. would be main characters as they are the core of the Avengers. On the Hydra side, characters like Baron Wolfgang von Strucker could be prominent. Also, there might be some original characters created specifically for the fanfiction, perhaps a Hydra scientist who is behind a new and dangerous experiment targeting the Avengers.
One possible plotline could be Percy trying to escape the Hydra experiment facility while using his demigod powers. He might have to fight off Hydra agents and other dangerous creatures they've created through their experiments.
It could be a Pokemon trainer who has a special connection with a particular Pokemon. This trainer gets recruited for an experiment because their Pokemon has shown some unique abilities. The trainer then has to balance their normal training routine with the demands of the experiment, all while protecting their beloved Pokemon from any potential harm that the experiment might bring.
I think Spider - Man would make an interesting main character. He's young and has a different perspective compared to the more experienced Avengers. His journey of growing up and becoming a more integral part of the team could be a central theme in the fanfiction. He also has his own set of personal problems like school and his relationships which could add depth to the story.
Captain America might be the main character. He represents the heart and soul of the Avengers in many ways. In this fanfiction, he could be the one leading the team through an emotional crisis, using his unwavering moral compass to guide them and protect the heart of the team and the world they are trying to save.
A new superhero created specifically for the fanfiction could be the main character. This character could have a power that is a combination of different Avenger's powers, like being able to have super strength like Hulk and also fly like Iron Man. Their unique abilities would draw the attention of the Avengers, making them the center of a harem - like story.
Well, it depends on the specific fanfiction. There are countless fanfictions out there, and while some may indeed feature Percy Jackson as being part of a Hydra experiment, others may not touch on this concept at all. It all comes down to the creativity and the plot that the individual fanfiction author has in mind. For example, one fanfiction might use this idea to explore Percy's powers in a new context, while another might use it to create a more complex and dangerous world for Percy to navigate.
Captain America could be the main character. Given his leadership qualities, he would be the one to step up and set an example when it comes to using the rectal thermometer. He would be the one to calm everyone down and remind them that it's for the greater good. He might also have some internal struggle with the whole idea, being from a more modest time, but he would do it anyway for the sake of the team.
The main character could be the original character (OC) who is the subject of the asari experiment. This OC could be from any species in the Mass Effect universe, like a human with a special gift or a krogan with an unusual resistance to certain biotics.