Well, perhaps his death in the Shrieking Shack could be part of a complex revenge plot. There could be an enemy who lures him there and manages to overpower him. This could be related to his past actions or allegiances. For example, if some Death Eaters still hold a grudge against him for his double - agent role, they might target him there.
Perhaps an old enemy from Snape's past, someone who has a long - standing grudge against him. This person could have tracked him down to the Shrieking Shack and finally got their revenge. It could be someone related to his days as a Death Eater or even from his school days when he might have made some enemies.
One possible plot development could be that Voldemort fully regains his power without Harry as an obstacle. The wizarding world would be plunged into complete darkness. His friends, like Hermione and Ron, might go into a deep state of despair and then form a resistance group. They would try to find other ways to defeat Voldemort, perhaps by seeking out more powerful magical artifacts or uniting with some previously neutral magical creatures.
One possible plot development could be how the wizarding world reacts to the loss of the so - called 'Chosen One' even as a baby. There might be widespread grief and fear among those who opposed Voldemort, as they had placed so many hopes on Harry. Another aspect could be how Voldemort's reign of terror continues without the threat of Harry Potter. He might become even more powerful and tyrannical, with no one to oppose him in the way Harry was prophesied to.
One possible plot development could be that his death shatters the Straw Hat crew. They might disband in grief, each going their own way. Zoro could become consumed with revenge, vowing to take on the Marines who were responsible.
One possible plot development could be that with Harry's death, Voldemort fully takes over the wizarding world. His reign of terror becomes absolute, and the remaining characters have to go into hiding or form a secret resistance. For example, Hermione might lead the resistance, using her intelligence to try and find a way to defeat Voldemort without Harry. Another aspect could be the emotional turmoil among the characters. Ron would be devastated, and his character could either sink into depression or be driven by a thirst for revenge. Ginny, too, would have to deal with the loss of her love and might become a more hardened and fierce fighter against the Dark forces.
One possible plot development could be that the Hidden Villages struggle to maintain peace without Naruto's influence. His death might lead to power vacuums and political unrest. For example, some villages may try to take advantage of Konoha's weakened state. Another aspect could be how his friends and family cope. His wife, Hinata, might have to raise their children alone, and his friends like Sasuke would feel a great sense of loss and perhaps guilt for not being able to protect him. The ninja world as a whole could also lose its hope symbol, and new, darker forces might emerge, thinking that without Naruto, they can carry out their evil plans more easily.
In this fanfiction, if Gohan dies in the Cell Games, perhaps the story could focus on how the other characters cope with the loss. For example, Chi - Chi could become a more hardened character, vowing revenge on Cell or any other threats. Piccolo might take on a more fatherly role to Goten, trying to train him to be as strong as Gohan was. And the Earth might be in a state of mourning, which could attract new villains who see it as a time of weakness.
In this fanfiction, it could also be that Harry's Gryffindor nature starts to rub off on Snape in some ways. They might have arguments about how things should be done, but through these interactions, Snape might start to see the value in Harry's way of thinking. And Harry, on the other hand, might learn some of Snape's more cautious and calculating ways, which could help him in his future battles.
The plot could involve the mistletoe having some sort of magical effect. Maybe it makes Snape and Hermione relive certain memories. As they do, they start to understand each other better. For instance, they might see how they both overcame difficulties in their pasts, and this new understanding could bring them closer together.
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.