The other superheroes in the Marvel universe would also be affected. They would likely feel a great sense of loss and guilt, especially if they could have helped but didn't. For example, Iron Man might blame himself for not providing enough technological support to Spider Man in his final battle.
His friends like Mary Jane would be devastated. She might lose her will to carry on at first, feeling like a part of her has died with Spider Man.
Well, if Spider - Man sacrifices his identity, it can make his friends and family feel a great sense of loss, even though they don't know exactly why. They might notice a change in him, like he's more distant, and it can strain their relationships.
Gibbs would likely be deeply affected. He might become more withdrawn and even more focused on getting justice for Tony's death. He may blame himself for not being there to protect Tony.
Sebastian and Flounder would be devastated. Sebastian might lose his sense of purpose as he was always there to guide and protect Ariel to some extent. Flounder, being Ariel's close friend, would likely be inconsolable. He may become more withdrawn and less adventurous. Ursula, if she is still alive in the fanfiction, might have a complex reaction. She could feel a strange sense of victory, but also a tinge of regret as Ariel was a worthy adversary, and without her, the underwater world becomes a bit duller.
The Young Justice team members would also be severely affected. Superboy might become more reckless in his actions, feeling that he should have been able to protect Robin. Aqualad could struggle with feelings of guilt for not having made better strategic decisions during the mission that led to Robin's death. And the team as a whole might become more fragmented as they each deal with their grief in different ways.
It could strengthen their relationships. For instance, the Avengers might gain a newfound respect for Spider - Man's abilities as they watch him in the PS4 world. They could start to see him as more of an equal, leading to closer teamwork in future battles.
If Spider - Man got new powers like telepathy in fanfiction, it could strain his relationship with some characters. They might feel he's invading their privacy. But with others, like Daredevil who also has enhanced senses, it could bring them closer as they share a new kind of understanding.
If Spider - Man gets new powers like mind - reading, it could strain his relationships. For example, his friends might feel violated if he accidentally reads their thoughts without permission. On the other hand, it could also strengthen his bond with some characters, like his mentor, as he can better understand their teachings.
In a 'Harry Potter Dies' fanfiction, the plot often takes a dark turn. The hope that Harry represented is gone. This could lead to the Ministry of Magic falling apart, as they had put so much faith in Harry. Hogwarts might also become a more dangerous place as the students lose their sense of security. The Death Eaters could become bolder, and the remaining good characters have to scramble to hold things together. It can also lead to new alliances being formed as characters who were once on the sidelines are now forced into the fray.
The symbiote often makes Spider - Man more aggressive. He might be quicker to anger and less patient. For example, he could snap at his boss J. Jonah Jameson more often.
It can also change the power dynamics. Spider - Man might become more isolated and have to rely more on his own wits and skills without the Black Cat's support. This could lead to him developing new abilities or strategies in the fanfiction. For example, he might have to form new alliances or learn to fight in different ways.