There might be some extremely dark and non - canon fanfictions out there with such a disturbing plot. However, this goes against the general spirit of the Harry Potter series. In the official story, Harry is a hero who overcomes great challenges. In a fanfiction with this idea, perhaps it could be due to extreme despair from losing too many loved ones or feeling an overwhelming burden of his destiny that he snaps and takes his own life. But again, this is a very unorthodox and sad take on the character.
Yes, there could be such a fanfiction in the vast expanse of the fan - created Harry Potter universe. But it's really a deviation from the core of the original story. Maybe in that fanfiction, Harry has been through some truly horrible and unthinkable events that make him lose all hope. For example, if all his friends were killed and he was left alone to face an unbeatable dark force, it could potentially lead him to this extreme decision. However, it's not something that most fans would like to see as it contradicts the image of the strong and resilient Harry we know.
One possible reason could be to hide his true identity. In the world of fanfiction, there might be threats or situations where he doesn't want to be easily recognized as Harry Potter. Maybe he wants to start anew, away from the fame and the constant danger associated with his name.
Well, it could be that he has lost all hope. In the fanfiction world, if the situation becomes so dire that he sees no way out for himself or the people he loves. For example, if Voldemort manages to gain complete control and Harry Potter thinks his sacrifice by taking his own life might be the ultimate solution to break Voldemort's power. He might also be suffering from post - traumatic stress after all the battles and losses, leading him to this extreme decision.
In the fanfiction, Harry Potter might live by himself because he is tired of the spotlight. After being in the public eye for so long, he desires a private life. He may also feel that living alone allows him to better understand himself and his powers. It could be that he has a prophecy or a personal quest that requires solitude. For example, he might be trying to master a very difficult and dangerous spell that he doesn't want anyone else to be in danger from if something goes wrong. Also, he could be exploring some dark corners of magic that the wizarding world might not approve of, and living alone gives him the freedom to do so without judgment.
One possible reason could be extreme self - sacrifice. Maybe he believes that by stabbing himself, he can save his friends or defeat Voldemort in a very unique way. For example, if there is a dark magic spell that can only be broken by his own life force.
One possible reason could be the overwhelming burden of his destiny. Harry has faced so many challenges and losses throughout his life. The death of his parents, the constant threat of Voldemort, and the weight of saving the wizarding world might have made him feel so tired and hopeless that he contemplates taking his own life.
One reason could be the shock of the revelation. Harry has always thought his parents were James and Lily. Discovering Snape is his father would be a huge shock, and he might isolate himself to process this new information.
One reason could be a powerful dark magic spell cast upon him by a new villain in the fanfiction world. This spell might be designed to make him disappear from the wizarding world entirely.
One possible reason could be that a powerful dark magic spell has been cast on him. Maybe a new dark wizard or witch, created specifically for the fanfiction, has found a way to make him vanish to cause chaos in the wizarding world. Another reason might be that Harry has chosen to disappear himself. Tired of the constant attention and danger, he decides to go into hiding, perhaps using some long - forgotten magic or a powerful magical object to conceal his presence.
In this type of fanfiction, one possible plot could be that Harry is under extreme mental pressure. Maybe he's constantly haunted by the deaths he has witnessed, like Cedric's death or the losses in the war. The pressure builds to a point where he feels like there's no way out and contemplates shooting himself as a way to end his pain.
Perhaps he's dealing with some sort of trauma. For example, after the many battles he's been through, like the fight against Voldemort, he may be suffering from post - traumatic stress disorder. To cope with this, he isolates himself from others as he doesn't want to burden them or he's just too caught up in his own dark thoughts.