Perhaps in this fanfic, a random accident could lead to Harry's death as a kid. For example, he could be exploring the Forbidden Forest on his own (as kids are wont to do) and stumble upon a very dangerous magical creature that he has no chance of fighting off. Without Harry, Dumbledore would have to re - think his entire strategy against Voldemort. The prophecy would then be left unfulfilled, and the balance of power in the wizarding world would shift in a very different way than what we know from the books.
One possibility could be that Voldemort manages to find and kill Harry much earlier. Maybe the protection spell that Lily cast fails due to some unforeseen dark magic interference. This would change the entire wizarding world. Hogwarts might be taken over by Death Eaters completely, and there would be no 'Boy Who Lived' to inspire hope. The Order of the Phoenix would likely be crushed much sooner, and the wizarding world would descend into a much darker and more oppressive state than in the original story.
It could be that in the fanfic, a betrayal within the wizarding world causes Harry's death. Maybe someone who was thought to be an ally, like a double - agent within the Order of the Phoenix, leads Voldemort right to Harry. His death as a child would mean that Ron and Hermione would grow up in a very different world. There would be no trio to fight against the dark forces. Instead, they might be forced to live under the thumb of Voldemort, and their own magical development and personalities would be shaped by this very different and much harsher environment.
One possible plotline could be that Harry Potter sacrifices himself to defeat an even more powerful dark wizard than Voldemort. Maybe this new enemy has a power that can only be countered by Harry's self - sacrifice, which would lead to a very bittersweet ending for the wizarding world.
One possible plot development could be that his friends are left to pick up the pieces. They might struggle with grief and guilt, thinking they could have saved him. Another could be that Voldemort finally takes over completely without Harry to oppose him, leading to a dark reign over the wizarding world.
Well, in this kind of fanfic, Harry could be neglected by Hogwarts staff. For example, teachers may be too preoccupied with other matters, such as political unrest in the wizarding world. Harry, feeling alone and abandoned, might venture into dangerous areas like the Forbidden Forest more often. He could encounter a powerful and malevolent creature that he's not ready to face, and ultimately die because there was no one to rescue him. Also, the Sorting Hat could potentially mis - sort him into a house where he doesn't fit in at all, and the neglect from his housemates could contribute to his downfall.
One possible plot could be that it causes chaos in the wizarding world. His friends like Hermione and Ron are devastated. They might start an investigation to find out the cause of his death, suspecting dark magic or a hidden enemy. This could lead to a series of adventures as they search for the truth.
A plotline could be that Ron is killed in a magical accident during an experiment gone wrong. This accident might be related to some new, dangerous magic that he was trying to master. His death would shatter the trio. Harry would feel guilty because he might have been involved in the experiment in some way. Hermione would be grief - stricken and would pour herself into research to try and understand what went wrong. The fanfic could then explore how the wizarding community reacts to Ron's death, with some blaming Harry and Hermione, and others mourning the loss of a great wizard. It could also show how Harry and Hermione have to grow and become stronger individually to face the challenges that come their way after Ron's death.
One possible plot development could be that Hermione is left with a deep sense of guilt and responsibility. She might then take on Harry's mission or cause in his memory. For example, if they were fighting against a new dark wizard, Hermione could become even more determined to defeat the enemy.
One possibility could be that he's facing a very powerful dark wizard. Maybe this wizard has some new and unknown dark magic. Harry tries his best to fight but is ultimately overpowered. His friends back at the Ministry are left in shock and grief, and the wizarding world has to deal with the loss of their hero.
If Harry dies instead of Cedric in fanfic, Hogwarts would be in a state of deep mourning. The entire wizarding world that had placed so much hope in Harry would be in shock. Voldemort would likely face less opposition in the short term as Harry was seen as the main threat to his return. Friends like Ron and Hermione would be devastated, and they might have to take different paths. Ron could become more withdrawn, and Hermione might focus all her energy on finding a way to avenge Harry. The story would also likely shift focus to Cedric, who would now carry the weight of the prophecy or the task of ultimately facing Voldemort, if there was such a concept in this altered universe.
One possible plot could be that Harry Potter, through some magical mishap or powerful spell, is transformed into a bride. Maybe he has to go on a quest to find a way to reverse the spell while dealing with the strange reactions of his friends and the wizarding world. For example, Ron might be completely confused and Hermione would be trying to find a solution in the library.
A possible plot could be that the dragon is a new, unknown and extremely powerful species. Harry is sent to investigate it but underestimates its power and gets killed.