It could also be that an outside force offers them something they desperately want, like the power to bring back a loved one who has died, but at the cost of turning evil. Naruto, who has always longed for his parents, and Hinata, who has a deep love for Naruto, might be tempted by such an offer. They then become agents of this outside force, causing destruction and mayhem as they try to fulfill their part of the bargain.
One possibility could be that they turn evil due to a powerful enemy using some dark magic or jutsu on them. This could make them lose their sense of self and start causing chaos in the Hidden Leaf. For example, they might start attacking their former friends and allies, believing they are now enemies.
Perhaps they turn evil because of a long - hidden conspiracy within the village. They discover some dark secrets about the village leadership and feel betrayed. In their anger and disillusionment, they decide to take revenge on the village that they once protected. This could lead to a very different Naruto and Hinata, ones who are now willing to use any means necessary to expose and destroy the 'corrupt' system.
One possibility is that an evil entity takes over Hinata. In the fanfic, Naruto could be the only one who can sense that Hinata is not truly herself. He starts to investigate and discovers a plot that involves an ancient evil. The story could revolve around Naruto's attempts to free Hinata from this control and save the village from the impending danger that the evil Hinata might bring.
Well, perhaps Asta could be corrupted by a powerful dark magic artifact. He might start to see his friends as obstacles in his quest for power and turn against them.
Their relationships with their friends would become extremely strained. Their former comrades would be shocked and saddened by their turn to evil. Naruto and Hinata would no longer be seen as the heroes they once were, and their friends would likely try to bring them back to the light, but it would be a difficult and dangerous task.
In a Naruto Hinata Evil Avatar fanfiction, the plot might involve an ancient evil entity that attaches itself to Hinata. As her avatar, she could start to manipulate the political situation in the Hidden Leaf. For example, she might spread false rumors or create unrest among the clans. And Naruto, being the hero he is, would have to figure out what's wrong with Hinata and stop her without hurting her too much.
One possible plot could be Pikachu getting influenced by a dark and powerful Pokemon. For example, a Darkrai might use its nightmare - inducing powers on Pikachu. This could make Pikachu start to attack other Pokemon and trainers without mercy. Maybe Pikachu would first target its own trainer, Ash, as it would be the most shocking turn of events. This would create a lot of chaos in the Pokemon world and force Ash and his other Pokemon friends to try and figure out how to save Pikachu from this evil state.
Well, it could be that Chichi is betrayed by her friends and that turns her evil. Maybe she discovers some dark secrets about her past that make her lose faith in good. Or perhaps she is influenced by an evil force that corrupts her pure heart.
It could also be that Naruto has a misunderstanding. He might misinterpret some actions of Konoha as being malicious towards him or his friends. As a result, he decides to oppose the village. However, as the story progresses, he realizes his mistake and instead works with Konoha to resolve the issues that led to the misunderstanding in the first place.
Sasuke could also become an antagonist in this scenario. If Naruto turns evil, Sasuke, who has his own sense of justice, would likely oppose Naruto. Their once - strong friendship would be shattered, and they would end up fighting each other, with Sasuke trying to stop Naruto from causing more destruction.
One possible plot could be Ruby being betrayed by her closest friends. Maybe she discovers a dark secret about the Huntsman academies that makes her question everything she has ever believed in. This disillusionment could start her on the path to evil as she feels that the system she has dedicated her life to is corrupt.
One possible plot could be that Naruto and Hinata find out about the pregnancy and they are both overjoyed. They start preparing for the baby's arrival, with Naruto being super protective of Hinata. He might go on missions less often to be around her. Hinata, on the other hand, could be seen knitting baby clothes and daydreaming about their future family life.