The plot could develop in a very different direction. For example, Voldemort might gain an advantage as Harry was seen as a major threat. Without Harry, the other characters would have to step up to fight against the Dark forces. Hermione and Ron might become more central characters in the fight against evil.
After Harry's death in the first task in fanfiction, the plot could shift towards a more complex political situation at Hogwarts and in the wizarding world. There could be accusations of incompetence or foul play regarding the Triwizard Tournament. Characters who were previously in Harry's shadow, like Neville, could start to emerge as important figures in the battle against the Dark Arts. Also, the remaining champions might have to face new and unexpected challenges as the tournament was already thrown into chaos by Harry's death.
If Harry dies in the first task in fanfiction, the plot would be full of twists. The Death Eaters might become more bold, thinking that the biggest obstacle to their master's return has been removed. On the Hogwarts side, the teachers would be in a difficult position. They would need to protect the students from the possible upsurge of dark activities. Meanwhile, some characters might start to explore magic in a more desperate way to find a way to counter the dark forces without Harry. And the relationship between different houses at Hogwarts could also change as they all deal with the shock of Harry's death.
One possible consequence could be chaos at Hogwarts. The school has high hopes for Harry in the Triwizard Tournament. His death would shock the students and teachers. The other champions might feel guilty or be blamed. Also, Voldemort's plans related to Harry would be disrupted, as he was supposed to be a major part in the wizarding world's future battles against the Dark Lord.
If Harry dies in the first task in fanfic, it would completely change the whole story. For one, Hogwarts would lose its hero. The Triwizard Tournament would be thrown into chaos. Cedric might become the sole focus then, but he also would be in shock as Harry was his competitor and also a fellow student. And Voldemort's plans related to Harry would be thwarted, at least for the time being, as he had some long - term designs involving Harry. It would also have a huge impact on Harry's friends, like Ron and Hermione. They would be devastated and might try to find out the real cause of his death.
Ron and Hermione would be completely shattered. Ron, who had been Harry's friend since the beginning, would probably be in denial at first. Hermione would likely try to figure out what exactly happened. Dumbledore would be solemn and would try to keep the school calm while also investigating the matter. Hagrid would be inconsolable, crying his eyes out. The other students would be in a state of shock and sadness. The teachers would also be deeply affected, especially those who had taught Harry or had some connection with him.
The story could continue by focusing on Ron and Hermione's journey to avenge Harry. They might discover some secrets that Harry was on the verge of uncovering before his death.
The plot could develop with Harry trying to get his things back from Molly, which might lead to a series of confrontations.
One way the story could develop is that after Harry meets his parents, they take him on a journey through his past. They show him the moments when they were still alive and how much they loved him even then. They might also introduce him to other deceased wizards and witches, and together they could form a new kind of family in the afterlife. The story could also have flashbacks to Harry's life at Hogwarts and how his actions led to this reunion in the afterlife.
In some fanfictions, Harry might struggle with PTSD after the third task. The trauma of facing Voldemort again could haunt him, causing nightmares and making him more withdrawn. He might also become more determined to defeat Voldemort, spending all his spare time studying dark magic defenses.
He might go on the run and form an alliance with some unlikely characters. For example, he could team up with some dark wizards who also have a grudge against Gringotts. But this would be a very risky move for him.
The plot could develop with Harry trying to find out the reasons behind Ginny's cheating. He might start investigating who the other person is and what led to her actions.
The playing of memories could also have a negative impact. If the memories are too distracting or if they make him overthink, it could lead to mistakes. For instance, if he gets too caught up in the memories of a champion who failed, it might make him nervous and cause him to make errors during the first task.