Well, if Spider - Man died in a Civil War fanfiction, it could be that his death serves as a catalyst for the end of the war. His death might make both sides realize how pointless their fighting is. Maybe the heroes would then come together to honor his memory and try to make amends. His friends in the superhero community, like Ned if he knew about Peter's identity, would be heartbroken. And villains might take advantage of the situation, thinking the heroes are weakened without Spider - Man, which could lead to new threats emerging in the fanfiction world.
He could become more withdrawn. Losing Aunt May, who was like a mother to him, would be a huge blow. He might isolate himself from his friends and even from his crime - fighting duties for a while as he deals with his grief.
If it's a crossover with the Fantastic Four, perhaps a cosmic entity is attacking Earth. Spider Man teams up with them to stop it. But during the battle, he's exposed to some deadly radiation from the entity. Despite the Fantastic Four's efforts to save him, his body can't withstand it, and he dies. His death could lead to the Fantastic Four creating new safety protocols for future battles.
One possible scenario could be that Spider Man sacrifices himself to save the city from a powerful and unstoppable villain. He might use all his strength and powers to defeat the enemy, but in the process, his body gives out due to the extreme exertion.
It could be Doctor Doom. He might be seeking to take over multiple universes in a crossover. Spider Man stands in his way, and Doom, with his superior intellect and powerful magic, manages to defeat Spider Man. His death would then be a huge shock to other heroes in the crossover, like the Avengers or the Fantastic Four who then have to avenge him.
New enemies could emerge. Maybe some villains would see his vulnerability after Aunt May's death and try to take advantage. As for alliances, he might team up more with other superheroes like Iron Man. He'd need more support now that he's lost his main source of emotional support at home.
The interaction of their powers would be fascinating. Harry's magic could be used to heal Spider - Man if he gets injured during a fight. Spider - Man's Spider - Sense could alert Harry of any oncoming danger, even magical threats that Harry might not be aware of immediately. Also, Harry could use spells to create distractions while Spider - Man uses his stealth to approach enemies unnoticed. This synergy between magic and superhuman abilities would create a very unique and exciting dynamic in the fanfiction.
In some fanfictions, Peter might die heroically while saving the city from a powerful villain like Venom. He could sacrifice himself to protect his loved ones and the innocent.
Yes, there are quite a few interesting 'Harry is Spider - Man' fanfictions. You can start by looking on popular fanfiction websites like Archive of Our Own or FanFiction.net. Some fanfictions might explore how Harry's magical abilities from the Harry Potter world could interact with Spider - Man's powers in unique ways, creating really engaging storylines.