Peter could sacrifice himself to stop a deadly virus from spreading. He might be a scientist who discovers that his own body can be used to create a cure, but it will cost him his life. So, he decides to go ahead with it to save the world.
Perhaps in this fanfiction, Peter sacrifices himself for the greater good of his community. He could be in a post - apocalyptic world where resources are scarce, and he gives up his life so that others can have a chance to survive. He might be a key figure in a resistance group, and his sacrifice becomes a symbol of hope for the survivors.
One possible scenario could be that Gwen is in danger from a powerful dark magic user. Merlin steps in to protect her, knowing that the only way to defeat the enemy is to sacrifice his own life force or magic. Another could be that Gwen is wrongly accused of a crime she didn't commit, and Merlin sacrifices himself to prove her innocence and save her from execution.
In fanfiction, Naruto sacrificing himself for Obito could be a very emotional and dramatic concept. It might show Naruto's ultimate selflessness, believing that Obito is worth saving at the cost of his own life. This could be due to Naruto seeing the good in Obito that others might not, like the part of Obito that was once a kind - hearted shinobi.
When Batman sacrifices himself in fanfiction, it can also be a way to explore the darker side of Gotham. Maybe his sacrifice was in vain, and the city falls deeper into crime and corruption. Or perhaps it leads to a new kind of hero emerging, inspired by Batman's last act. It could also show how the villains react, some might be glad that their nemesis is gone, while others may feel a strange sense of loss as Batman was always a worthy opponent.
One scenario could be that they are facing a powerful monster. The monster is about to strike Annabeth, and Percy jumps in front of her at the last moment, taking the fatal blow. Another possibility is that they are in a dangerous situation like a collapsing building or a sinking ship, and Percy uses his powers to ensure Annabeth's escape while he stays behind and perishes.
Perhaps in the fanfiction, Naruto gives his life energy to Boruto to save him from a deadly curse. Boruto then has to deal with the newfound power within him, which is a mix of his own and his father's. He may struggle to control it at first but eventually learns to use it for good. This could also lead to a rift between Boruto and some of the villagers who blame him for Naruto's death.
In such a fanfiction, the plot could involve Naruto sacrificing himself to save the Hidden Leaf Village from a powerful and seemingly unstoppable enemy. Maybe it's a new, more menacing form of the Akatsuki that has emerged with a doomsday - like jutsu. Naruto, being the hero he is, decides that the only way to protect his friends and the village is by using a self - destructive jutsu that nullifies the enemy's power but at the cost of his own life. His sacrifice could lead to a period of mourning in the village, with his friends like Sasuke feeling guilty for not being there to prevent it and vowing to carry on Naruto's legacy of peace.
In some fanfictions, if Harry Potter sacrifices himself, it could lead to a dark and desolate wizarding world. His friends would be left to pick up the pieces, mourning his loss deeply. For example, Hermione might be driven to find a way to reverse his sacrifice through her vast knowledge, while Ron would be filled with a sense of vengeance towards the forces that led to Harry's death.
One possible plot could be that in a final battle against an extremely powerful enemy, Naruto realizes that the only way to save Hinata and the entire village is by using a forbidden jutsu that will cost him his life. He makes this sacrifice with a smile on his face, knowing that Hinata and the others will be safe. Hinata is heartbroken but also determined to carry on Naruto's legacy of protecting the village.
In fanfiction where Batman sacrifices himself, a frequent theme is the power vacuum. With Batman gone, who will control the criminal underworld? Will new heroes or villains rise to power? Another theme is the emotional turmoil of the supporting characters. Alfred, for example, has to deal with the loss of someone he considered like a son. And the theme of hope can also be explored. Does Batman's sacrifice give the people of Gotham a new sense of hope, or does it shatter their faith in heroes?