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 character would become more menacing. The Vasto Lorde transformation might bring out a darker side of Naruto.
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.
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.
His relationships would surely be strained. His friends might be afraid of him or try to reason with him, but Naruto's violent nature could drive a wedge between them. For instance, Sakura might be horrified by his new - found aggression and try to stay away, which is a big change from their usual dynamic.
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.
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.
Harry's character could become more confident. With the new title of Lord Black, he has a certain status and power. This might make him less hesitant in making decisions. For instance, when dealing with the Ministry of Magic, he could be more assertive in demanding changes for the betterment of the wizarding community.
His character would become more detached. Percy is usually very involved and emotional in his relationships, but as Death, he would need to be more aloof. He can't be too attached to the living as his new role demands a certain level of impartiality towards life and death.
He becomes cold towards others. He no longer shows the warm smiles and friendly greetings that he used to. Instead, he might ignore people or give them cold stares.