How would the character of Harry Potter change in a fanfiction where he raises a Mosasaurus?

He would become more responsible. He has to take care of another person now, so he can't be as reckless as he sometimes was. For example, he'd think twice before running into danger because he has his sister to consider.

Harry might develop a different set of values. Flitwick has his own way of looking at the wizarding world. Under his care, Harry could grow to value knowledge and magical finesse more than he does in the original story. This could lead to a Harry who is more diplomatic and less impulsive when dealing with other wizards and witches.

He would probably be more conflicted. His moral compass would be constantly tested. He might have a natural inclination towards power, like his father, but also have the good heart he developed growing up. So he'd be constantly fighting within himself.

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 He might be more withdrawn as he tries to come to terms with it.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.

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.

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.