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.
Dumbledore would feel a great sense of loss and guilt. He had always seen Harry as the key to defeating Voldemort. His reaction could be to go into seclusion for a while to think about what went wrong. The other Hogwarts professors would be in shock. Hagrid would be heartbroken and might even leave Hogwarts in his grief. And the Death Eaters would be jubilant, but also a bit wary as they know that there could be unforeseen consequences to Harry's death.
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.
Hermione would likely be devastated. She might go into a deep state of mourning, but also use her intelligence to try and figure out what led to Harry's death. Ron would be angry and heartbroken at the same time. He'd probably want to seek revenge if there was someone or something responsible.
Ron would be completely shattered. Harry was his best friend, and he would likely feel guilty for not being able to protect him. He might become reckless in his attempts to avenge Harry. Hermione would be grief - stricken but also determined. She would pour herself into finding a solution to the mess left behind. Ginny would be heartbroken. She might initially withdraw but then become a strong advocate for justice, using her own skills and magic to fight against Voldemort's regime.
Nagisa would be completely devastated. She has a very deep connection with Tomoya, and his death would likely cause her to sink into a deep depression. She might even lose the will to live, especially if it happened suddenly. For example, if he died in an accident, she would be left with a sense of emptiness and longing for him.
The characters would be devastated. Grover, Percy's best friend, would be heartbroken. He might lose his ability to find Pan because of the emotional turmoil. His search for Pan was always connected to his friendship with Percy, and without Percy, he could be lost.
Ruby would be deeply saddened. She might blame herself for not being able to protect Blake. Weiss would probably be in shock at first, then become more determined to fight against whatever caused Blake's death. Yang would be furious and seek revenge. She has a very close bond with Blake, and her death would likely fuel Yang's anger towards the enemy.
Sakura would be devastated. She has always seen Naruto as a dear friend and teammate. She would probably blame herself for not being strong enough to prevent his death. Sasuke, on the other hand, might feel a deep sense of loss and anger. He might go on a solitary journey to find out who was responsible.
Uraraka would be heartbroken. She was one of Deku's closest friends. She might lose some of her usual cheerfulness and become more focused on finding out who or what was responsible for his death. She could also struggle with her own self - confidence in using her quirk, as Deku was always an inspiration to her.
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.