His character would likely become more conflicted. Harry was always a symbol of good in the original series, but under Grindelwald's influence, he'd be exposed to different ideas of power and control. He might start to question his own beliefs.
Harry's character development could be a journey of self - discovery in a very different sense. Instead of growing into the hero against Voldemort, he'd be growing in the shadow of Grindelwald. He could become more cynical as he sees the darker side of magic through Grindelwald's eyes. And he might develop a more independent streak, not relying on the traditional Hogwarts values but rather on what Grindelwald teaches him, which could be both good and bad for his character.
Harry's character would likely become more conflicted. He'd be exposed to Grindelwald's radical ideas, which might make him question the values he learned at Hogwarts. His sense of right and wrong could be blurred, and he'd have to struggle to hold onto his true self.
His character would likely become more edgy and darker. Growing up with demons, he'd be exposed to a lot of negative and cruel things, which would change his view of the world.
Harry would develop a more diverse set of values. Ahsoka comes from a different cultural and moral background in the Star Wars universe. So, he might start to see magic and power in a different light. He could become more in tune with nature and the Force, which would add new layers to his character. Also, his sense of loyalty would expand beyond his friends at Hogwarts to include those he meets in the Star Wars universe through Ahsoka.
Harry's character would likely become more independent and self - reliant. Alduin may not coddle Harry like some of his Hogwarts mentors did. He'd have to learn to fend for himself in a strange new world. His sense of adventure would be heightened as he explores Alduin's domain. Also, his view of magic would expand greatly, which could make him more confident in his abilities.
His character would probably become more humble. Elves are not as prideful as some wizards, so Harry might adopt that trait.
Harry's character would likely become more worldly. Living with the Delacours, he'd be exposed to different magical cultures. His confidence might grow as he is part of a loving family environment instead of the neglectful Dursleys. He could become more refined in his magic usage, learning from Fleur's elegance in spell - casting. Also, his sense of self - worth would increase, which could make him a more assertive leader in the fight against Voldemort.
She would likely start off very influenced by Grindelwald. Maybe she'd be a bit cold and calculating like him at first. But as she experiences more of the world, she'd become more empathetic. For instance, if she meets a group of oppressed wizards, she'd start to question Grindelwald's views.
Grindelwald's character might also develop in fanfiction by having a redemption arc. He could be influenced by Harry Potter's ideals of love and friendship. For instance, after a series of battles and discussions with Harry, he starts to question his own beliefs and gradually moves towards the light side.
Harry could also develop a more self - reliant and perhaps a bit of a loner personality. Since Grindelwald is not as nurturing as some other potential guardians, Harry would have to fend for himself more often. This would make him stronger in some ways but also more aloof from others, as he would be used to relying on his own skills and judgment rather than on a community or friends.
His character would likely become more confident. With Wonder Woman as his adoptive mother, he'd have a strong role model. He might be less reserved and more assertive in using his powers. For instance, he'd see how Wonder Woman fearlessly faces her enemies, and he'd be inspired to be bolder with his magic.