If Harry grew a beard in a fanfiction, his personality could also shift a bit. He might become more introspective. The beard could be a physical manifestation of his inner growth. He could be less impulsive, taking more time to think things through, like an old wizard who has seen it all. Also, he might be more reclusive, using the beard as a sort of barrier between himself and the outside world that has always had such high expectations of him.
If Harry grew up in Japan in fanfiction, his view of the magical world would be shaped by Japanese culture. Japanese art forms like origami could have magical applications. His spells might be chanted in Japanese. His enemies could also be different, perhaps based on Japanese dark magic concepts. He would grow up in a society that values harmony, so his approach to conflict, both in the magical world and personal relationships, would be more about mediation and finding common ground rather than direct confrontation like in the original story.
He would probably be more otherworldly. Harry might have an air of mystery around him that the original Harry didn't have. His actions could be more guided by a sense of divine purpose.
He would likely become more conflicted. Harry, who was always on the side of good, would now have to deal with this dark lineage. He might be more withdrawn as he tries to come to terms with it.
He would probably be more in tune with nature. Instead of just having a connection to Hedwig, he might be able to communicate with all kinds of animals. So he could be more of a naturalist wizard.
If Harry became a succubus, his magical abilities would transform. He could gain the ability to influence others' emotions on a deeper level. His personality might become more complex as he tries to balance his old self with the new instincts of a succubus. He may also become more isolated as some in the wizarding world might fear or misunderstand his new form. But at the same time, he could also find new friends who are more accepting of his unique situation.
He would become more of a space - faring leader. His focus would shift from the wizarding world on Earth to the cosmos. He'd probably be more open - minded about different cultures and species, just as he was about different wizarding houses at Hogwarts.
He would likely be more conflicted. Harry was always a morally upright character, but with Thanos as his father, he'd have to battle inner demons. He might be more powerful physically and have a darker side to his personality that he constantly has to keep in check.
He would be much more physically powerful. Instead of relying just on magic, he could use his Saiyan strength to solve problems. For instance, he might be able to break through magically locked doors with his bare hands.
Harry may become more empathetic towards outcasts. Growing up in an orphanage, he is surrounded by other children who have been abandoned. This could make him more understanding of those who are on the fringes of society, not just in the Muggle world but also in the wizarding world. For instance, he might be more inclined to befriend house - elves or other marginalized magical creatures. He could also be more protective of his friends, as he values the relationships he forms in the orphanage more since they are his only real family for a long time.
His character would likely be distorted. He might become more cynical about relationships in general. Since Hetai fanfiction often portrays relationships in a rather improper and unrealistic way, Harry might lose his sense of the true, deep - seated values of friendship and loyalty that are so central to the original story.