Perhaps in the fanfiction, Percy is under some sort of dark influence. This could be from a new, unknown magical force. This influence makes him see Jason as a threat to his friends or himself, so he attacks Jason. Jason, on the other hand, is initially confused but then tries to fight back to defend himself while also trying to figure out what's wrong with Percy.
It could be that there is a competition between them, like for a leadership position in a group or for the affection of a certain character. Percy feels that Jason is using unfair means to win, and his temper gets the best of him. So, he decides to beat up Jason. As the story unfolds, they both learn valuable lessons about competition, friendship, and trust.
In this fanfiction, perhaps there is a misunderstanding between Luke and Percy. Luke might think Percy has betrayed him in some way, like siding with the wrong people in the context of their fictional world, and thus resorts to violence by beating him up.
Percy could be the instigator if he has a moment of rage or is misinformed. His impulsive nature might lead him to start the fight without fully understanding the situation.
One possible plot could be that they have to team up to stop an ancient evil that is rising. Each of them brings their own unique powers to the table. Percy with his control over water, Jason with his power over the wind and lightning, and Nico with his ability to manipulate the shadows. They journey to different realms to find the artifacts needed to defeat this evil.
Yes, there are quite a few. You can find some on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Percy Jackson Beats Jason' and you'll get a list of relevant stories. Some might focus on a battle between them where Percy's skills and wits help him overcome Jason.
Well, it could be about a misunderstanding. Maybe there's a rumor that Percy has done something bad to Jason's friends, so Jason challenges him to a fight. Percy, being Percy, doesn't back down and they start fighting. In the end, they realize it was all a big misunderstanding when the real culprit is found.
Maybe Sakura gets angry at Naruto for some misunderstanding, like he accidentally ruins one of her important medical experiments. So she decides to beat him up to teach him a lesson.
The plot might involve Percy and Jason having to adapt to the new and chaotic rules of the Chaos realm. They could discover new powers within themselves as they are exposed to the wild and unpredictable energy there. They might also meet old enemies who have also found their way into this strange new world, leading to some epic battles and unexpected alliances.
One possible plot could be that Jason is really shy about his crush at first. He tries to be around Percy more often, like joining the same quests or training sessions. He might secretly do nice things for Percy, like leaving his favorite food at his cabin without saying who it's from.
Well, in such a fanfiction, perhaps Sasuke has some sort of plan that involves Hinata in a negative way. Naruto discovers this and decides to beat up Sasuke to protect Hinata. It could also be part of a bigger struggle where Sasuke's actions are seen as a threat to the future Naruto envisions with Hinata, so Naruto takes matters into his own hands to stop him.
One possible plot could be that they discover they are brothers through a series of magical events. For example, a powerful oracle reveals the truth. Then they have to deal with the shock of this new relationship while also facing their common enemies. They might train together to combine their unique powers and protect their world from threats.