One reason could be extreme guilt. Maybe he failed to save someone important and can't bear the burden of that failure. In some fanfictions, if he accidentally caused harm to his loved ones, like Aunt May getting hurt because of his superhero activities, the guilt might be overwhelming.
Another aspect could be isolation. Peter often keeps his identity a secret, and this can lead to a great sense of loneliness. If in a fanfiction he feels like he has no one to truly talk to or connect with about his dual life, he might sink into despair and consider taking his own life. He's constantly juggling normal life and superhero duties, and if he feels he can't handle it anymore, that could be a trigger.
Some writers might do it for shock value. They want to create a very different and extreme take on the character to get a strong reaction from readers.
One possible reason could be extreme loneliness. In the Merlin universe, if Harry felt he didn't belong or was constantly ostracized, it might lead him to such a dark place. Another reason could be a sense of powerlessness. Maybe he was faced with a seemingly unbeatable foe and thought death was the only escape.
One possible reason could be extreme stress. Peter Parker has a lot on his plate, being Spider - Man and having a normal life. If in the fanfiction he faces a series of really tough situations like failing to save someone important or being hunted by a very powerful enemy, the stress might get to him and lead to self - harm as a way of coping. Another reason could be feelings of isolation. Even though he has friends, he might feel like no one truly understands the dual life he leads, so in the fanfiction this could drive him to such a desperate act.
He might think it's not in line with the real Steve. Fanfiction can be quite far - fetched sometimes.
Well, it might be an exploration of the psychological toll of being a superhero. Peter Parker constantly faces danger, loss, and has to keep his identity a secret. Writers may create 'suicidal peter parker fanfiction' to show how all these factors could potentially break him. Also, in the context of fanfiction, it could be a way to subvert the typical heroic narrative and show a more vulnerable and broken side of the character. However, it's a very heavy and potentially triggering topic.
Well, one reason could be that he's on a secret mission for S.H.I.E.L.D. that requires him to go undercover and cut off all contact. Maybe he's investigating a new super - villain threat that's too dangerous to let anyone know about.
Perhaps he is under the influence of dark magic. There could be a spell or a curse that makes him lose his will to live. Or, in the fanfiction world, he might be bullied or persecuted to an extent that he sees no way out but to end his own life.
A possible plotline could be Peter deciding to break away from the Avengers or any big superhero group he's associated with. He might feel that he's not growing as much as he could on his own. So, he sets out to be a solo hero again, facing new challenges without the backup of the group.
Maybe it's due to a new and powerful enemy's attack. In fanfiction, authors might create unique villains with abilities that specifically target Peter's weaknesses. For example, if the villain has the power to disrupt Spider - Man's enhanced senses, it could cause Peter to be disoriented and ultimately collapse. Another aspect could be that Peter overuses his powers without proper rest, which exhausts his body and causes him to collapse.
It could also be a way to subvert the typical superhero narrative. Usually, superheroes are invincible and always triumph. By writing about Peter Parker committing suicide, it challenges the norm and makes readers think about the fragility of even the most iconic characters. It forces the audience to consider the toll that being a hero can take on a person's mental and emotional state.