Well, if Cedric survived, their relationship could become more of a mentor - mentee situation in reverse. Harry, having faced Voldemort multiple times, could teach Cedric about the true nature of dark magic and how to defend against it better. Cedric, on the other hand, could teach Harry about the importance of patience and fairness which are Hufflepuff traits.
In a crossover where they are transported to another world, their relationship might develop out of necessity at first. But as they face challenges together, they would start to respect and admire each other more. Cedric might see Harry in a new light, not just as the Boy Who Lived, but as a true friend. And Harry would appreciate Cedric's calm and collected nature in the face of danger, which is different from his more impulsive Gryffindor friends.
It could start with simple exchanges in the hallways or during classes. They might share a smile or a quick conversation about the latest magical theory they learned. Then, they could be paired up for a project in Herbology, where they start to really get to know each other. Cedric's gentlemanly nature would make him very respectful towards Harry's sister, and she would be drawn to his kindness and confidence.
If they travel back to a time when Ginny was much younger, like when she was a first - year and Harry was a bit older (due to time travel), Harry could become a sort of protector and mentor to her. This would build a different kind of bond. He could help her discover her magic in new ways and she could show him the innocence and wonder of Hogwarts from a young student's perspective. As she grows older in that time period, their relationship could shift from mentor - mentee to a more romantic one in a very unique way.
He'd likely be more inquisitive about different forms of magic. Instead of just relying on the spells taught at Hogwarts, he'd constantly seek out new magus - based knowledge.
In fanfiction, their relationship could develop more positively from the start. Instead of the initial animosity, Snape could see Harry's potential right away and take him under his wing. This would lead to Harry trusting Snape earlier and having a stronger mentor - mentee bond.
Well, in canon, Harry is mainly involved with Ginny. But in a fanfiction with Daphne, their relationship would be more of a slow - burn mystery. Since Daphne is from Slytherin and Harry has his Gryffindor ideals, there would be a lot of initial conflict and mistrust. Their relationship might develop out of a mutual need to survive in a darker wizarding world, rather than the more typical romantic beginnings in the original story.
In canon, Harry and Lucius are enemies. But in a Fem Harry Potter scenario, the relationship could start off with Lucius underestimating her because she's a girl. This could lead to her getting the upper hand in some initial encounters. For example, she might use her charm or a different kind of magic that Lucius isn't expecting. Their relationship could develop into a more complex dance of power and manipulation compared to the straightforward enmity in the original story.
Harry would likely become more feared by some in the wizarding world. Since the Basilisk is often seen as a terrifying and dangerous creature, his connection to it might make others view him with suspicion. He would also have to grapple with the darker side of magic that the Basilisk represents, which could make him more brooding and introspective.
In their friendship, they were more like comrades. But as betrothed, there would be a new level of intimacy. They might start to notice little things about each other in a more romantic way. For example, Harry might be more aware of Hermione's beauty when she's reading, and Hermione might find Harry's leadership in a different light, seeing it as a quality for a future partner.
He'd be more confident. With a loving mother around, he wouldn't have the insecurities that came from growing up with the Dursleys.
His magical abilities might develop in a different way. The Malfoys could introduce him to different types of magic or magical artifacts. Maybe he'd learn more about the Dark Arts in a different context, not for evil purposes but just to understand it better. He could also become more skilled in areas like Occlumency earlier on, since the Malfoys might see it as an important skill to protect their family secrets. His relationship with his Gryffindor traits would be tested. He might still have his bravery, but it could be expressed in different ways, like standing up to the Malfoy family's wrongdoings.