If the new timeline is more dangerous, Harry might become more cautious. He has to be careful not to make mistakes that could cost him his life or the lives of others.
In a different timeline, Harry may face different kinds of hardships. If he has to deal with a lot of betrayal in this new timeline, he might become more distrustful. On the other hand, if he experiences a lot of love and support, he could become more open and friendly. His personality would be shaped by the new environment and experiences he encounters in this other timeline.
He could become more confident. For instance, if in the new timeline he has some special powers or abilities that he didn't have in his original one. He might start to believe in himself more and take on challenges more boldly. Also, if he meets different people who encourage him in new ways, this could also boost his confidence.
His personality might also be influenced by the people he meets in the alternate universe. If he meets a group of very kind and peaceful wizards, he could become more laid - back and positive. On the other hand, if he is surrounded by cruel and calculating wizards, he may become more withdrawn and calculating himself as a form of self - protection.
Naruto could become more curious. A different world means new things to explore, new cultures, and new powers. He would be eager to learn about everything, which could make him seem more inquisitive than he already is. He might start asking a lot of questions to understand how this new world functions.
Percy Jackson's personality could change quite a bit in another world in fanfiction. His sense of humor might be affected as the new world may not have the same cultural references that he's used to in his own world. He could become more solitary as he tries to figure out this new place on his own. However, his underlying sense of justice would likely remain. He would still be drawn to help those in need, but he might go about it in different ways. He might also develop a new sense of pride in being able to adapt and survive in this new world, which could change how he presents himself to others.
His personality would likely become more erratic. The Joker's influence is all about chaos and anarchy. Harry might start to laugh at inappropriate times and find pleasure in causing trouble just like the Joker. He could lose his sense of empathy as he is constantly exposed to the Joker's cruel and inhumane behavior.
His personality might become more traditional in some ways. Since the founders are from an earlier time, their values could rub off on him. He might be more reserved like some of the older wizards.
His personality would probably be more cold and calculating. Voldemort's influence would make him less empathetic. He might be more ruthless in achieving his goals.
Well, Harry's personality would be a blend of his old self and his new Uchiha nature. He'd likely be more intense. The Uchiha are known for their strong emotions and passion. Harry might become more focused on achieving power to protect those he cares about, which was also a part of his personality as Harry Potter, but it could be amplified. He might also develop a bit of an air of mystery, as Uchiha are often seen as mysterious in the Naruto world. His sense of humor might change too, becoming a bit drier perhaps, more in line with the stoic nature of some Uchiha.
Well, in the new timeline, Harry could find that Voldemort has already won. This would mean he has to figure out a way to either change the past to prevent this future or find a way to defeat Voldemort in this new, much more difficult situation. It would be a huge challenge for him.
With Ron, they might not be as close as they were at Hogwarts. Ron might be a bit jealous if Harry does really well in college. But on the other hand, they could also bond over missing Hogwarts and their old adventures.
He might become more reserved. Shinobi are often taught to keep their emotions in check, so Harry would be less likely to be as openly angry as he sometimes is in the original story.