When Naruto becomes a bijuu in fanfiction, his life is turned upside down. He has to deal with the instincts of the bijuu which might conflict with his own values. For example, if the bijuu has a natural inclination towards destruction, Naruto has to fight against that. His role in missions would change. He might be sent on more dangerous and specialized missions that require his new powers. His living situation could also change. He might need a special place to stay that can accommodate his new form and its needs.
His life changes drastically. Firstly, his social status within the village would be very different. People might fear him initially. His relationships with friends like Sasuke and Sakura would also be affected. They would have to adapt to this new Naruto. His training regime would change completely as he has to learn to control his new bijuu form. He might have to isolate himself at times to avoid causing harm.
When Naruto becomes the Nine - Tails in fanfiction, his life is completely transformed. Socially, he might be isolated at first because others are intimidated by his new form. Emotionally, he has to come to terms with being a part - fox, part - human entity. He might have new memories or instincts that he has to learn to control. Physically, he has the power to destroy or protect on a massive scale. His daily life would be different as he has to adapt to his new body and powers, and he would have to find a new balance in his relationships with Sasuke, Sakura, and the rest of the village.
His life would become much more complex. With multiple bijuu inside him, he has to manage more power and more voices in his head.
His power level would skyrocket. Naruto already had the power of the Kyuubi within him, but as a kitsune, he'd have a more direct connection to that power. He could access it more easily and use it in ways he couldn't before. For instance, he might be able to transform into a full - kitsune form with ease, and in that form, his speed, strength, and durability would be greatly enhanced.
Naruto might become more calculating. Since Mewtwo is very intelligent and has powerful psychic abilities, Naruto would have to use his mind more. He would think before acting, unlike his impulsive self in the original series. This change could make him a better strategist in battles, but it could also lead to misunderstandings with his friends who are used to his more straightforward and impulsive nature.
Naruto's personality could shift towards being more reserved. As a Shinigami, he has to deal with the weight of handling souls and the concept of death. This could make him think twice before acting impulsively like he used to. He may also develop a more empathetic side towards those who are about to die or have lost loved ones, as he now has a closer connection to the afterlife.
Naruto's character would change in several ways. Firstly, he would become more strategic. As a lord, he has to plan for the long - term development of his land, which requires thinking ahead. His impulsiveness would be curbed as he has to deal with the complex web of politics. He would also grow in terms of wisdom. He would learn from his experiences and the advice of his advisors. His charisma would be used in a different way. Instead of just inspiring his ninja comrades, he would need to inspire all his people. His sense of justice would expand from individual cases to the overall fairness of his domain, and he would strive to make his territory a model of a just society.
He becomes more serious. Gone is the Naruto who is always cracking jokes.
His relationship with magic could also transform. Without the support of the wizarding community, he may start to explore magic in his own way. He could discover new spells or magical abilities that are not taught at Hogwarts. This newfound knowledge might be a double - edged sword. On one hand, it could help him survive as an outcast. On the other hand, it could further isolate him as it makes him even more different from the others.
His character would become more menacing. The Vasto Lorde transformation might bring out a darker side of Naruto.
If Naruto becomes a Hunter Nin in fanfiction, his personality would change significantly. He'd be more calculating. His usual impulsive nature would have to be toned down because one wrong move as a Hunter Nin could mean disaster. He might also become more solitary, used to working alone in the shadows rather than in a team. His sense of humor might also be more subdued as he takes on this serious and dangerous role.