He'd be tougher. Hiei's no - nonsense attitude would rub off on him. Harry would be more likely to take risks without hesitation.
Harry's magic would develop in a new way. He'd probably use it more instinctively and aggressively. Since Hiei is used to fighting for survival, Harry would adopt a similar approach to using his powers. He might not wait for permission or follow the traditional wizarding rules when it comes to using magic. Instead, he'd use it to his immediate advantage, much like Hiei does with his demon powers.
Harry's character would be more attuned to the deeper magics. He would be less likely to jump into things without thinking. Since Flamel is a master of alchemy, Harry might be more interested in the scientific aspects of magic. He would also have a greater respect for life and magic's power, as Flamel, with his long life, would instill in Harry a sense of wonder and caution about the forces they deal with.
He'd be more disciplined. His character would be shaped by military values. He'd be less likely to act impulsively and more likely to think things through strategically.
His character would become more rugged. Instead of the somewhat sheltered and naive Harry we see at the start of the original series, he'd be tough - minded. Burt Gummer's influence would make him more of a fighter from the get - go.
Harry Potter's character would likely develop a stronger sense of independence. Since Jack Frost is often portrayed as a solitary figure, Harry might learn to rely on himself more. He could also develop a sense of wonder for the natural elements, especially ice and snow. His values might shift towards a more elemental view of magic, and he might be less interested in the politics and social hierarchy within the wizarding world. His sense of justice could still be strong, but it would be more in line with the unyielding nature of ice, being very firm and unwavering.
Harry's character would undergo a significant transformation. The Cullens' values of self - sacrifice and protecting the family would influence him. He'd likely become more empathetic towards non - human beings. His magic might be used in more creative ways to adapt to the Cullens' lifestyle. For instance, he could use magic to make their home more vampire - friendly. His confidence would grow as he learns from the Cullens' strong family bond.
He would likely be more confident. Growing up with gods would give him a sense of self - assurance that he lacks in the original story. He might be less hesitant in using his powers.
His character would be more assertive. He'd be used to taking action quickly due to his Warrior upbringing. He might be less hesitant in difficult situations compared to the original Harry.
His character would be more stable. Without the Dursleys' abuse, he would be less angry and more trusting.
In this kind of fanfiction, Harry would develop a very different set of values. Growing up with pirates, he'd value things like loot, loyalty among the crew, and freedom of the seas. His sense of justice might be more like a pirate's idea of justice - rough and ready. He'd be bolder in his actions and less likely to wait for permission or guidance. For instance, if he saw something wrong at Hogwarts, he'd take matters into his own hands immediately rather than go through proper channels. He'd also have a more salty language perhaps, and his interactions with other students would be interesting as he tries to fit in while still holding onto his pirate - raised ways.
In this fanfiction, Harry's character would develop in a very different direction. He would likely be more of an outcast. Growing up with a Nundu, he wouldn't have the normal social interactions a wizard kid has. So, he could be more withdrawn and less communicative. But at the same time, he would be very self - reliant and have a strong survival instinct.