Highlight the reactions of the people he leaves behind. Show MJ's heartbreak, Aunt May's grief and Ned's disbelief. This will make the sacrifice more poignant. Maybe MJ refuses to believe he's gone at first and keeps waiting for him to come back.
Show his internal struggle before making the sacrifice. Let readers see his thoughts about leaving behind his friends, family and the city he loves. For example, he could be thinking about all the future moments he'll miss with MJ, like their dates or growing old together.
Use flashbacks of his life. Remind readers of all the good he's done, his growth from a nerdy kid to a hero. When he sacrifices himself, it will feel like the end of a beautiful journey. For instance, flashbacks of him getting his powers, his first time saving someone, and his relationships developing can all add to the emotional depth.
Perhaps in the fanfiction, Peter Parker sacrifices himself to protect his loved ones. A powerful villain has targeted his aunt May, MJ and Ned. Peter realizes that the only way to stop the villain from harming them is to give up his own life, so he does something heroic and self - sacrificing like using his body to shield them from a deadly attack.
One way is through internal monologues. Peter can have long internal conversations with himself, debating where to go on the 'date', what to wear, etc. This would show his different aspects interacting.
To make it impactful, show the reactions of his loved ones in detail. For example, Aunt May's heartbreak and MJ's grief. Their pain can really drive home how much Peter meant to them.
Well, his friends could find out. For example, Ned or MJ might stumble upon him in a vulnerable state. This would then lead to a deepening of their relationships as they try to help him. They could encourage him to seek professional help or just be there for him emotionally.
Fanfiction involving such a dark topic can be quite disturbing. I don't really recommend seeking it out as it goes against the positive essence of the character. Peter Parker is typically a symbol of hope and heroism in the Spider - Man universe.
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.
Another way is to join fanfiction communities or forums dedicated to Spider - Man. There, you can ask for recommendations of powerful Peter Parker fanfiction. People in these communities are usually really helpful and can point you to some hidden gems that you might not find through a simple search.
Another character could be Aunt May. She has always been an important figure in Peter's life. When he faints, she could be extremely worried and try to figure out what's wrong with him, perhaps even blaming herself for not taking better care of him.
In many fanfictions, Snape's sacrifice for Harry is often explored in great emotional depth. One common aspect is how his love for Lily Potter extended to protecting Harry. His self - sacrifice is shown as a redemptive act, finally revealing his true nature to Harry, which was full of love and loyalty all along.
There are also fanfictions where his attempt is not successful, but it has consequences. He might end up in a hospital, and then have to deal with the fallout of his actions. People around him might be angry, sad, or confused, and he has to face their reactions while also trying to figure out how to move forward and get better.