His self - control would improve. Given Fleur's Veela charm, Harry would need to constantly keep his wits about him. This would be a big step in his character development as he has had issues with his temper in the past. He would also become more diplomatic. He has to deal with Fleur's family, who might be a bit skeptical of this young English wizard protecting their daughter. So he would learn to communicate better, and this would expand his social skills within the wizarding world. Also, his sense of responsibility would grow as he is now accountable for Fleur's safety, which could make him more reliable in future adventures and relationships.
Harry's character could develop in terms of his cultural understanding. Fleur is from a different wizarding culture (French - based). As her bodyguard, he would be exposed to her traditions, language, and magic. He might start to pick up some French phrases and understand the nuances of Beauxbatons magic. Emotionally, he would become more empathetic towards Fleur's situation. He would see her not just as a beautiful Veela but as a person with her own dreams and fears. This new - found empathy could also make him a better friend and ally to others in the wizarding community.
Harry might become more refined. Fleur has a certain elegance about her, and growing up with her could rub off on Harry. He could become more polite and cultured in his ways.
At first, their relationship might be a bit strained. Harry is used to his own space and friends, and Fleur has her own circle. But as they live together, they'll start to respect each other's differences. For example, Fleur might be more flamboyant in her magic use, while Harry is more practical. They'll start to see the value in each other's approaches and become closer friends.
Often, Harry's sense of responsibility grows. He starts to see the marriage contract as not just a burden but also an opportunity to create a new life for himself and Fleur. Fleur's personality may develop in a way that she becomes more protective of Harry. For example, when they face opposition from the wizarding community about their contract, she stands up for them. She also might help Harry to overcome his insecurities about being in a relationship with someone as glamorous as her.
At first, they might be at odds with each other. Fleur could think Harry is too impulsive, while Harry might find Fleur a bit too haughty. But then, when they are forced to work together on a mission, they see the good in each other. Fleur realizes Harry's selfless nature, and Harry sees Fleur's intelligence and determination. This new - found respect leads to a romantic relationship and ultimately marriage.
He could develop a darker side to his personality. Learning from Voldemort, he may become more ruthless in achieving his goals, even if those goals are still ultimately good. For instance, he might be more willing to use unethical means to defeat other dark wizards. But at the same time, he would also be constantly struggling against this new - found darkness within him. He would be in a battle not just with external enemies but also with his own changing self.
Fleur could be shown as more independent and brave. Since she's taking it upon herself to save Harry, it shows her courage. Maybe she becomes more confident in her own abilities outside of the Triwizard Tournament context.
He'd likely be more humble. Elves are not boastful, and growing up with them would instill that in Harry. He might be less likely to seek fame or glory like in the original story.
His character would likely become more well - rounded. Since the Grangers are intellectuals, Harry might become more studious. He'd be exposed to different ways of thinking. For instance, instead of just relying on magic for solutions, he'd learn to use logic and knowledge like the Grangers do.
Harry's character would likely be a mix of confusion and determination. He'd be confused by Voldemort's teachings which go against his natural inclination towards good. But his determination to find his true self would remain. He might develop a sort of duality, acting one way around Voldemort and his followers, but secretly being someone else.
Harry would likely become more in tune with magic on a deeper level. Since Fawkes is a magical being full of ancient magic, Harry might gain new insights into spells and wizardry.