In this kind of fanfiction, there could be various scenarios. Maybe Tails gets into a fight with a really powerful enemy, like a new super - villain. The villain might have some sort of weapon or power that nearly defeats Tails. For example, a weapon that can disrupt his flight or his mechanical abilities.
There could also be the villains. Depending on the context of the fanfiction, it might be Dr. Eggman. He's always trying to cause trouble for Sonic and his friends, and he could be the one behind the situation where Tails almost dies. So Dr. Eggman would be a main character on the opposing side.
Fanfictions about Naruto being neglected and nearly dying can be quite intense. Some might depict him being pushed to the brink by the lack of support from the village. For example, he could be deprived of proper training or basic necessities. However, these situations usually lead to Naruto's character growth in a different way than in the original series. He might form unexpected alliances with outcasts or find new powers within himself.
One interesting Tails Dies fanfiction could be one where his death leads to Sonic's journey of self - discovery and growth. Sonic has to face the reality without his friend and in the process, he becomes more determined to fight against the forces that caused Tails' death.
In some fanfictions, Hermione could be in a situation where she's exploring a dangerous, ancient magical ruin. There could be a series of traps, and she almost dies when she accidentally triggers a deadly one. Her intelligence and quick thinking, along with the help of her friends, might be the only things that save her in the end.
Definitely Naruto. He's always been there for Sakura, no matter what. He would use his Nine - Tails chakra if he had to in order to save her. Sakura's female friends like Ino could also play a role in her rescue. Ino is a skilled ninja in her own right and has a deep friendship with Sakura. And don't forget Tsunade. As the Fifth Hokage and Sakura's mentor in the medical field, she would do everything she could to save Sakura's life.
The plot might develop by showing how the world changes without Tails. Maybe his inventions were crucial for the protection of their world, and now they have to find new ways to survive. It could also involve other characters trying to bring Tails back through some magical or technological means.
It might be a creative way to rewrite the Sonic story in a more mature or complex way. By having Tails die, new storylines can be created that focus on themes like grief, loss, and redemption. For example, Sonic could struggle with guilt over not being able to save Tails, and this could be the central theme of the fanfiction.
In some fanfictions, Tails' death might be a catalyst for the other characters to come together. Maybe Tails dies while protecting the Chaos Emeralds, and this unites Sonic, Knuckles, and Amy to safeguard the emeralds and prevent further chaos. They might then go on to honor Tails' memory in different ways throughout the story.
One possible storyline could be that Tails gets involved in a dangerous adventure where he sacrifices himself to save his friends. For example, he might be facing a powerful new enemy that has invaded Sonic's world. Tails, being the intelligent and brave fox he is, uses his mechanical skills to create a diversion that allows Sonic and the others to escape, but in the process, he is fatally injured. Another storyline could be related to a disease outbreak in his world. Tails tries to find a cure but ends up being infected himself. As he weakens, he uses his last moments to pass on his research to the other characters so they can continue the fight. A third storyline could be a time - travel gone wrong. Tails might be sent to a different era where the conditions are too harsh for him to survive, and his death in that era has a profound impact on the future when Sonic and the gang discover what happened.