Perhaps in a different take, they are tricked into believing that their side is in the wrong. They might be deceived by false information about a supposed conspiracy within their own village. So, thinking they are doing the right thing, they side with the 'enemy', which is seen as a betrayal by their comrades.
One possibility could be that in a ninja world setting, Sakura and Hinata are forced to betray their friends due to a powerful enemy's blackmail. Maybe the enemy has kidnapped their families and threatened to harm them if they don't cooperate. This could lead to a rift in their relationships with Naruto and the others.
Hinata could lose her usual shy and gentle demeanor. The act of betrayal might force her to be more assertive, but in a negative way. She might become more defensive and less empathetic towards her former friends.
Perhaps in the fanfiction, Konoha betrays Sakura by spreading false rumors about her. They could say she's been collaborating with the enemy, which would damage her reputation not only in the village but also among her friends. This would lead to her being ostracized and feeling deeply betrayed by the place she once called home.
It could also be a misunderstanding. Hinata might be under some sort of mind - control or false impression. For example, an illusion is cast on her that makes her believe Naruto has become evil. As a result, she takes actions against him that he perceives as betrayal. In this case, once the truth is discovered, they would likely reconcile.
In some fanfiction, this could happen due to a misunderstanding. Maybe Hinata is forced into a situation where she has to seem like she's betraying Naruto. For example, she could be blackmailed by an enemy who threatens the safety of the village or her family. Another possibility is that there is some sort of mind - control involved that makes her act against Naruto.
One possible plot could be that Percy, who has some hidden motives or is being manipulated, leaks the Avengers' secret strategies to their enemies. Maybe he was promised power or something in return. This would lead to the Avengers facing unexpected and difficult battles as their foes seem to anticipate their every move.
One possibility could be that Ginny is influenced by dark magic or a powerful enemy. Maybe she's forced to betray Harry to protect her family. For example, Voldemort's remaining followers could threaten to harm her family if she doesn't spy on Harry and give away his secrets. Another idea is that there could be a misunderstanding. Ginny might think she's doing the right thing for Harry, but it ends up looking like a betrayal. For instance, she could be trying to help him by making a deal with someone she believes is good, but who actually has ulterior motives.
One possible plot could be that Ash is forced to give up Charizard in a high - stakes Pokémon battle. Maybe a powerful trainer challenges Ash and demands Charizard as the prize if he loses. Ash, being a proud trainer, doesn't expect to lose but due to some unforeseen circumstances, like a new and unknown Pokémon move used by the opponent, he loses the battle. Charizard, being sent to the new trainer, initially resists but is somehow forced to obey. This makes it seem like Charizard has betrayed Ash as it has no choice but to follow the new trainer's commands.
One possible plot could be that Ash and Brock are lured into a false sense of security by a powerful new trainer. This trainer seems friendly at first but then secretly uses their Pokémon to undermine Ash and Brock during important battles. Ash and Brock might start to suspect something when their Pokémon keep getting mysteriously weakened. Eventually, they realize they've been betrayed when the trainer reveals their true intentions of trying to take over their region's Pokémon league.
One possible plot could be that Cynthia, perhaps in a quest for power or influenced by some dark force, betrays Ash. Maybe she steals his Pokémon to use in her own battles or to offer to a powerful villain in exchange for something she desires, like rare Pokémon or access to a powerful training ground.
In a 'Sakura and Hinata joins Akatsuki' fanfiction, perhaps they are forced to join. The Akatsuki could be holding something or someone important hostage. Sakura might be trying to find a way to break free from the inside, using her intelligence and combat skills. Hinata, on the other hand, would be more conflicted due to her gentle nature. She might befriend some of the more empathetic Akatsuki members and try to persuade them to change their ways.