One option could be a rogue agent from within Shield who has turned against the organization. This agent could be jealous of Hawkeye's newfound status in Shield and tries to undermine him at every turn while also planning some sort of major heist or attack on Shield's assets. They might have some sort of high - tech weaponry that Hawkeye has to outwit with his arrows.
Well, one possible plot could be that Hawkeye is initially a lone agent but gets recruited by Shield. He might be hesitant at first, but then discovers a conspiracy within Shield that he has to help expose using his sharp shooting skills and street smarts. Maybe he teams up with some classic Shield agents like Coulson and they go on a mission to take down a powerful enemy who is secretly infiltrating Shield.
The main villain could be an escaped criminal who stumbles upon the house thinking it would be a good place to hide. But when he realizes there's a kid alone, he decides to take advantage and ransack the place. The kid has to use his wits and the resources around the house to defeat this dangerous villain.
A dark demigod who was once rejected by the gods and now wants to use the Staff of Fire to take revenge. He could be really powerful and have the ability to control shadows, using them to his advantage against Percy and his friends.
Loki could be a likely villain. He has a history of mind - controlling people and causing chaos within the Avengers. He might see Hawkeye as a useful tool to disrupt the team again. His mischievous nature and magic powers would make it easy for him to brainwash Hawkeye without being detected at first.
A musical - themed villain could be interesting. This villain uses 3D sound waves as weapons and creates hypnotic music to control people in the Spy Kids' world. The Spy Kids would have to break the spell of the music and find a way to silence the villain's dangerous tunes.
The new villain could be a former student of the Nutty Professor who felt wronged in some way. Maybe the student was expelled unfairly (in his mind) or didn't get enough credit for his contributions to a project. So, he decides to seek revenge on the professor by using his own knowledge of the professor's research to create chaos in the university and in the professor's personal life.
In many Avengers Hawkeye origin fan fictions, Hawkeye often starts as a skilled archer in a rough background. Maybe he grew up in a small town where he learned archery as a form of self - defense or hunting. His natural talent led him to be noticed by certain individuals or organizations, which gradually drew him into the world of superheroes.
A voodoo priestess who is using the zombies to carry out her revenge on the islanders for past wrongs.
One great Hawkeye Kate Bishop fan fiction is 'The Archer's Ascent'. It delves deep into Kate's training journey, showing her determination to become as skilled as Clint Barton. The story is filled with action-packed scenes where she faces various challenges and overcomes them with her wits and archery skills.
It could be Darkseid from the Wonder Woman universe who somehow manages to enter the Sailor Moon world. He would be a powerful and menacing villain, using his powers to try and take over both worlds. His dark energy would be a contrast to the light and love - based powers of Sailor Moon and Wonder Woman.