It could be a new super - villain introduced in the fanfiction. Maybe a villain with powers that are specifically designed to counter Spider - Man's. For instance, a villain who can manipulate technology and uses it to disable Peter's suit and then delivers a fatal blow.
The Vulture could also be responsible in a different way than in the movie. Maybe in the fanfiction, he teams up with other villains and they come up with a more elaborate plan to kill Spider - Man. They could set a trap that Peter falls into, leading to his death.
In some fanfictions, it might be one of Peter's friends or classmates accidentally. For example, if they were involved in some scientific experiment gone wrong that Peter was trying to help with, and it ended up causing his death. It would add a tragic twist to the story as it was an unintended consequence.
Doctor Octopus is also a likely candidate. His mechanical arms and high intelligence could give him an edge. He could manipulate a situation where Peter is caught off - guard and unable to defend himself, resulting in his death.
One aspect could be the emotional impact. Fans often have a strong connection to Peter Parker. His death in fanfiction might be a way to explore grief and the aftermath among the other characters in the Spider - Man universe. It could also be a means to create a new narrative direction, like how the remaining characters step up in his absence.
Liz Allan is often overlooked. We could see her having a more complex relationship with Peter. Maybe she has her own dreams and ambitions that conflict with Peter's superhero life. And what about the other students in Peter's class? Each of them could have their own stories and personalities that could be developed in fanfiction. For example, one of the students could be secretly a big fan of Spider - Man and start to suspect that Peter is the hero.
Well, you could write a fanfiction where Peter Parker has to team up with a villain from a different universe who is also trying to get back home. They form an unlikely alliance and during their journey, Peter learns more about the multiverse and his own powers. It would be full of action and character development.
Another possibility is a former crewmate turned traitor. This crewmate could have been jealous of Edward's leadership and the share of the loot he got. So, the traitor could plot with other pirates or even the enemy. They could stage a mutiny at a crucial moment, like when they are about to face a big battle or are in the middle of a difficult sea journey. During the mutiny, the former crewmate could be the one to deliver the fatal blow to Edward.
In some versions, it could be a former ally who has been corrupted. This character, once on Ahsoka's side, has now turned against her due to some external influence or personal greed. Their knowledge of Ahsoka's strengths and weaknesses would make them a formidable opponent, and they could be the one to cause her death.
A new character could be introduced as his dance partner. Maybe a transfer student from another country who has a unique dance style. This character could bring a fresh perspective to Peter's life, teaching him new moves and also learning about his world as Spider - Man. They could form a fast friendship based on their shared love for dance.
One option is Pepper Potts. She is intelligent and has a strong will. In a fanfiction, she might see the potential in Peter and they could develop a relationship. Pepper could also help Peter deal with the business side of being a superhero, like Tony Stark did, and they could fall in love over time.
It could be the Green Goblin. He's always been one of Peter's toughest foes and poisoning him would be a devious way to take him down.
It could be a vengeful criminal that Spider - Man has put away in the past. This criminal has spent years in prison plotting his revenge and finally gets the chance when Peter is vulnerable. Maybe he manages to ambush Peter in an alleyway while he's on his way home from school or work.