Well, in a lot of these fanfictions, Stiles can get beat up due to his own recklessness. He might be so determined to solve a mystery or help his friends that he doesn't think about the consequences and ends up in a dangerous situation where he is outnumbered and beaten up. Also, there could be miscommunication. Maybe someone thinks he has done something wrong when he actually hasn't, and they take matters into their own hands and beat him up.
One possible reason could be a power struggle. Gerard might see Stiles as a threat to his own authority or plans within the story's context.
One possible reason could be that he's gotten on the wrong side of a powerful client. Maybe he uncovered some shady business deals of the client during a case, and the client decided to take revenge by having him beaten up. Another reason might be related to his past. If some of his old associates from his pre - Harvey days found out he was now working in a high - profile law firm, they could be jealous and target him.
One popular 'Stiles gets beat up' fanfiction might be found on Archive of Our Own. You can search for tags like 'Stiles Stilinski' and 'beat up' to narrow down the results. There could be various interpretations in different fanfics, some might be related to a supernatural attack while others could be more mundane bullying scenarios.
There might not be a whole lot of mainstream 'Stiles gets beat up by Gerard' fanfiction. However, you could join some fan groups or forums dedicated to the relevant fandom. Fans there might be able to point you towards some such stories or even have written some themselves.
It could be an antagonist character in the Septiplier fanfiction world. Maybe someone who has a grudge against Jack for some reason, like a rival in a game or a love interest situation gone sour.
One possible reason could be that she's in the wrong place at the wrong time. Maybe she stumbles upon a group of antagonists who target her because she's known for her association with certain powerful characters. For example, if there are enemies of her friends or family, they might use her as a way to send a message.
In some fanfiction scenarios, Sakura could be under the influence of a dark power or a curse. This power might be corrupting her mind and making her lash out at Naruto for no real reason. It could also be a case where Sakura is trying to prove herself as a strong kunoichi and Naruto is just in the wrong place at the wrong time, so she uses him as a target to show off her skills.
Sasuke could be one. Given their complex relationship, there could be a situation where Sasuke's newfound power or different ideology leads him to fight and beat Naruto in a fan - made story.
Perhaps the fanfiction is following a specific plot arc that doesn't naturally involve Stiles. Like if it's a story about a new villain in town and the existing characters are dealing with it in a way that doesn't require Stiles' skills or presence. Also, some writers might be influenced by popular trends in the fandom that don't feature Stiles, and they go along with that to attract more readers.
One possible plot could be that Percy is targeted by a group of jealous rivals. Maybe they envy his status or abilities in the story's world. They might ambush him in a secluded place like an alleyway near his school or in a forest he often visits.