Harry would likely have a different set of values. Yugi had a strong sense of justice and friendship in Yu - Gi - Oh. As Yugi's son, Harry would place even more emphasis on these values. He might be more open to different cultures and beings, since the Yu - Gi - Oh world has a wide variety of characters. Also, his appearance might be a bit different, perhaps having some features that are more in line with the Japanese - inspired look of the Yu - Gi - Oh characters.
If Harry was Yugi's son in a fanfic, his relationship with magic would be different. Instead of just relying on spells and potions, he would also incorporate the power of the duel monsters. His confidence would come not only from his magical abilities but also from his connection to the Yu - Gi - Oh cards. He would be more of a hybrid between a wizard and a duelist. His social skills might also be different as he would attract different kinds of friends. Some might be interested in his unique heritage and the powers he could potentially bring from both worlds. He would also have to deal with the expectations of two very different fan bases, those of Harry Potter and those of Yu - Gi - Oh, which could add more complexity to his character development.
He'd probably be more confident. Knowing he's the son of Uther Pendragon would give him a sense of noble lineage. He might be more assertive in his actions and decisions, and less likely to tolerate injustice.
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 He might be more withdrawn as he tries to come to terms with it.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.
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.
He would be much more physically powerful. Instead of relying just on magic, he could use his Saiyan strength to solve problems. For instance, he might be able to break through magically locked doors with his bare hands.
If Harry was the son of Loki, his confidence would likely take a different turn. Instead of the somewhat hesitant confidence he has in the original series, he might have a more brash and calculated confidence. He would be more aware of his potential power and be more willing to take risks. His relationships with his friends would also change. Some might be drawn to his new, more exciting and dangerous side, while others might be put off by the Loki - like traits emerging in him. He would have to learn to manage these new aspects of his character while still maintaining his core identity as Harry Potter.
Harry would likely have a different sense of self - worth. Knowing he is the son of a powerful underwater hero like Aquaman, he would carry himself with more pride. He might also be more in tune with his emotions, as the ocean is often associated with depth of feeling. And his magical abilities could be enhanced in ways related to water, like creating more powerful water - based spells. He could also be more of a loner, as his unique heritage might make it hard for others to fully understand him.
He would be more aggressive. As a Baratheon, he'd inherit that family's bold and sometimes brash nature. Instead of the somewhat reserved Harry we know, he'd be more likely to take immediate action, whether in a duel or in dealing with a problem at Hogwarts.
He might be more confident in dealing with non - magical people. Since Pepper is used to operating in a world full of normal humans, Harry could have a better understanding of how muggles think. Also, he might be more tech - savvy, using modern devices to aid his magic or to keep in touch with his wizarding friends in a different way.