The plot would change drastically. Naruto's evil transformation would mean that his goals are no longer about protecting Konoha and his friends. His actions would likely be focused on self - gain or revenge. This would lead to new alliances and enmities. For example, he might team up with anti - Konoha forces. His evil actions would also force his friends to reevaluate their own beliefs and values. They would have to decide whether to fight him or try to redeem him. And the overarching theme of the story would shift from one of hope and perseverance to one of despair and conflict.
She would likely become more cynical. Instead of seeing the good in people, she'd be constantly looking for their weaknesses. For example, she'd no longer offer help to struggling students but rather use their difficulties against them. Her once - warm and friendly nature would be replaced with a cold and calculating demeanor.
Well, in such a fanfiction where Naruto becomes evil, it would be a total upheaval of the Naruto universe we know. His dark side could lead to alliances with villains like Orochimaru. He might start to hunt down those he once considered friends. His change could also be a result of some great betrayal, and his quest for vengeance would make him a very dangerous force. This would not only change the story's dynamic but also the fates of all the characters involved.
If Naruto becomes involved with Slenderman in a fanfiction, his usually cheerful and determined personality might become darker. He could be more withdrawn as he grapples with the strange and often terrifying aspects of Slenderman's world.
His ninjutsu might be enhanced. For example, his Rasengan could gain new properties due to the influence of Campione powers. His speed and strength, which were already considerable in the Naruto world, could be further increased. Maybe his ability to sense danger, which was related to his ninja training, could be upgraded to a more supernatural level in the Campione world.
He could become less impulsive. Seeing Himawari's more calculated and careful approach to things, Naruto might learn from her. He may start to think things through more before acting, just like he admires in Himawari. Also, he would be more of a cheerleader for her, boosting her confidence which in turn would change his own character to be more of an encourager in general.
One possibility is that Naruto could be betrayed by the village he loves so deeply. Maybe false accusations of being a traitor are made against him. This heartbreak and sense of injustice could be the catalyst for his turn to evil. He might then use his powerful jutsu against Konoha, believing that they don't deserve his protection anymore.
His relationship with Sasuke would be really interesting. Since Sasuke has his own complex connection to the Uchiha clan and Madara, Naruto becoming a Madara fan could either bring them closer together in understanding the Uchiha's past or drive them further apart if Sasuke doesn't agree with Naruto's new - found admiration. Maybe Naruto would start to push Sasuke towards a more 'Madara - like' view of power and revenge.
His relationship with Sakura would change a lot. Sakura might be initially scared of Naruto's fox form, but as she realizes it's still him inside, she would start to see him in a new light. She could become more protective of him. With Kakashi, Kakashi would be more cautious and observant, trying to figure out how to help Naruto control his new form. And with his rivals, they might either be more envious or more afraid of him now that he has this unique transformation.
In a fanfiction where Naruto becomes Hokage early, the story would take a different turn. His early leadership could mean a faster implementation of his ideals. He might start projects to improve the living conditions of the common people in Konoha right away. However, he would also face opposition from the more traditionalist ninja who might think he's too young and inexperienced. His journey as Hokage would be a roller - coaster of learning, making mistakes, and growing into the role much earlier than expected.
His personality might become more cautious. Since he has a greater responsibility as a guardian, he can't be as reckless as he was sometimes in the original Naruto series.