Maybe in the fanfiction, Spider - Man discovers that Female Carnage has a hidden side. She has some sort of soft spot for the innocent people in the city, which is contrary to what her violent nature implies. This discovery leads to an unexpected bond between them and they start to work together more closely.
One possible fanfiction could involve Spider - Man having to face off against Female Carnage in a battle that takes place in a crowded city. He might initially underestimate her power due to her being a female version of Carnage. But as the fight progresses, he realizes she's just as dangerous and has to use his wits and agility to try and subdue her without causing too much destruction to the city.
Well, it would be a very dark turn. Spider - Man is known for his heroism and moral code, while Carnage is a brutal and chaotic villain. If he became Carnage in fanfiction, he might start to use excessive violence and lose his sense of right and wrong. His relationships with his friends and family would be severely strained. For example, Mary Jane might be terrified of him, and his friendship with Harry Osborn would be in jeopardy. Also, the city he protects would be in chaos as he starts to go on rampages instead of saving people.
For Carnage's character arc, you could make him initially just a mindless force of destruction. But as Spider - Man continuously thwarts his plans, he begins to develop a sort of grudging respect for the web - slinger. He might then start to target Spider - Man in more complex ways, not just brute - force attacks. This shows growth in his character from a simple villain to one with more depth. Also, you could have him face a situation where he has to choose between his own survival and the continuation of his chaos - creating ways, which could lead to an interesting internal conflict.
If Spider - Man becomes Carnage in fanfiction, the story might develop as he begins to target his former allies. He could go after the Avengers, thinking they are a threat. The other heroes would be reluctant to fight him at first, believing there's still some of Spider - Man in there. Meanwhile, a new character could emerge, someone who has a connection to the original symbiote that created Carnage and has the knowledge to potentially save Spider - Man. This would lead to a race against time to stop 'Carnage - Man' before he causes too much destruction.
In a more cooperative scenario, Spider Man's web - shooting could be used in combination with Female Carnage's shape - shifting. For example, she could transform into a large structure and Spider Man could use his webs to anchor it or create a web - based mechanism around it. Their powers could also clash in a way that creates interesting visual and story - based effects, like when Spider Man's web gets caught in Female Carnage's symbiotic mass and she uses it against him.
Even one of Spider - Man's fellow superhero friends might betray him. Maybe they get jealous of Spider - Man's popularity or feel that he is getting all the credit for their team's successes. This internal betrayal would add a lot of drama and conflict to the fanfiction story.
One possible fanfiction could be about Peter Parker using his Spider - Man abilities in a snow - covered city during a cold snap. Maybe he has to deal with villains who are taking advantage of the difficult weather conditions. For example, a villain could be using the snow and ice to create dangerous traps for the citizens, and Spider - Man has to swing through the icy streets to stop them.
Peter Parker as Spider - Man is obviously a popular character. He's the main protagonist. Venom is often a popular character in fanfictions as well. His dark and menacing nature contrasts with Spider - Man's heroic side. Mary Jane might also be popular as she is an important part of Spider - Man's story. Another could be Harry Osborn, as his relationship with Peter is always an interesting aspect to explore in fanfictions.