His sense of responsibility would grow even more. Knowing the future, he would feel an even greater obligation to protect everyone. He might be constantly on guard and take on a more leadership role among the Z - fighters, guiding them in their training and battle strategies. He would also probably be more patient with the younger versions of his friends and family, understanding their potential better.
When Gohan goes back in time, he could become a bit more of an enigma to the people around him. His knowledge and power from the future would set him apart. He might be more secretive about some things to avoid disrupting the timeline too much. But at the same time, he would be more open about important things like potential threats. His relationship with his father, Goku, would also change. Instead of being the son that Goku sometimes has to protect, he could become more of an equal or even a mentor in some ways, teaching Goku things that he learned in the future.
Well, perhaps Gohan goes back in time to save his father, Goku, from some early danger. He could then train alongside Goku when they were younger, leading to a much stronger Goku earlier in the timeline. This could also have a ripple effect on the relationships within the Z - fighters. For example, with a stronger Goku earlier, their battles against the Red Ribbon Army or other villains might be much easier and quicker.
When GT Goku goes back in time in fanfiction, his character may change in many ways. He could be more of a planner, thinking ahead about how to avoid the mistakes of his original timeline. He might also be more protective of his friends and family, knowing what they had to endure in the future. His sense of responsibility would likely grow, as he now has the power to shape the past and create a better future. This could lead to him being more involved in the political and social aspects of the Saiyan and Earth communities, rather than just focusing on his own training and battles.
In some fanfiction ideas, when Vegito goes back in time, his power could be affected by the different energy levels in the past. Maybe the ki in the past is purer, which could either enhance his power further or require him to adapt in a new way. Also, if he has to hide his true power to not disrupt the timeline too much, he might have to find new ways to use his skills subtly.
His return could have a huge impact on the power balance. Since Future Gohan is a powerful fighter, his presence could tip the scales in battles against villains. For example, in fights against the Saiyans or the androids, his skills and experience could give the Z - fighters an edge.
His character could become more humble. Going back in time and seeing the past versions of people and events might make him realize how much he has changed over the years. He may also become more cautious. Knowing the consequences of certain actions from his original timeline, he'll be more careful with his decisions in the past. For example, he might think twice before revealing his identity as Iron Man too soon.
His relationship with his father Goku might change. Goku would probably be both curious and a bit worried. He'd want to help Gohan understand and control his new form. With Piccolo, he might become more of an equal in terms of being an 'outsider' since Piccolo has always been different. And with his friends, they might be initially scared but then come to rely on his new wolf - enhanced abilities.
Gohan's relationships would develop differently. Let's say he goes back to when he was a kid and meets his father, Goku, at a younger age. He'd have a different kind of bond with him. He could teach Goku things he learned in the future, and this would change how they interact. Also, his relationship with Piccolo would be altered. He might be able to train with Piccolo in a more advanced way earlier, leading to a stronger bond based on mutual growth and respect. Overall, Gohan would become more of a proactive and influential character in the past.
His character can become more assertive. As a Saiyan in fanfiction, Gohan may no longer hold back his power or his opinions. He could be more vocal about his goals and desires, rather than being the quiet and reserved character we often see in the original story.
Gohan may become more confident in relationships. In a harem situation, he has to deal with multiple people interested in him, which could boost his self - assurance.
His character might become more empathetic. In the female universe, he could be exposed to different ways of thinking and feeling among the female characters, which would make him more understanding.