One possible plotline could be that Naruto is constantly shunned and mistreated by the village despite his efforts to protect it. This continuous rejection could gradually turn his heart cold and make him seek revenge. He might start using his powerful jutsu against those who once wronged him, like attacking the Hidden Leaf's leadership.
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 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.
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.
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.
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 be Yuno. Normally they are friends, but if Asta turns evil, Yuno might be the one to oppose him. Yuno has his own strong magic and a sense of justice that would make him a natural adversary.
If Naruto turns into a Digimon in a fanfic, it could also be due to a curse or a dark magic. He might start off confused and disoriented in his new form. However, being Naruto, he would quickly adapt. He could form an unlikely alliance with some Digimon characters. His Digimon form might have some sort of unique ninja - like attacks that are a combination of his original jutsu and the digital powers. For example, his Shadow Clone Jutsu could be transformed into a digital clone attack where the clones are made of digital energy.
In a fanfic, Naruto turning into a Pokemon might also lead to some comical situations. Imagine Naruto, now as a Pokemon, trying to communicate with his friends in Konoha. He might have to use Pokemon sounds and gestures at first, causing a lot of confusion among his comrades. But eventually, they figure out a way to understand him, and it becomes a fun adventure for everyone.