His life would change drastically. He would be surrounded by different magic and different values. Instead of the traditional Hogwarts education, he'd get a more spiritual and otherworldly form of teaching. He might not be as naive about the dark side of magic as he was in the original story.
He might become more reserved. Shinobi are often taught to keep their emotions in check, so Harry would be less likely to be as openly angry as he sometimes is in the original story.
His relationships would be very different. He might find it hard to relate to other wizards at first. He'd be more used to the company of dragons, so he might seem a bit aloof to humans. But he could also form very deep and loyal friendships because of his dragon - influenced sense of loyalty.
His story would be drastically different. He might not have the same fear of Voldemort as he would be in a different environment. Instead, he could be facing threats related to Rias' world like other devil clans or powerful supernatural beings.
Harry would probably be more physically fit and combat - ready. Sasuke would train him in ninja ways, so he'd be better at hand - to - hand combat compared to the regular Harry. His approach to facing enemies would be more direct and less about relying solely on magic. He might also be more independent, as Sasuke is not one to encourage over - dependence on others.
His personality would be more aggressive. Yautja are hunters, and growing up with them, Harry would adopt their aggressive nature. He would be more direct in his actions and less likely to hesitate.
He'd be tougher. Hela's not one to coddle, so Harry would have to grow up fast.
Harry would be less socialized in the typical human way. He might not understand things like friendship the same way. He could be more territorial and protective. His magic might also be affected. He might use it more instinctively, like using a spell to protect his 'territory' which in this case could be the area where his wolf pack lives.
If Harry Potter was raised by Natsu, his personality would change drastically. Natsu is a very passionate and hot - tempered character. Harry would be influenced by this passion and would be more driven in his pursuits. He would no longer be the meek boy who was bullied by the Dursleys at the start. Instead, he would be more confident and assertive. His sense of justice would also be more like Natsu's, which is more about immediate action rather than following a set of bureaucratic procedures. He would probably have a stronger sense of loyalty towards his friends as well, because Natsu values friendship above all else and would instill this value in Harry.
He'd likely be much more morally ambiguous. Harry would probably have less regard for the rules and traditions of the wizarding world.
His view of family would be different. Vikings had a strong sense of clan. So instead of longing for a family like he did in the original story, he'd be part of a large Viking family unit. His magical abilities might be more of a mystery to the Vikings around him, and they could either fear or revere him for it.