Maybe in the fanfic, Aunt May's death is the catalyst for Peter to take on a more serious and darker approach to fighting crime. He could start to question his no - killing rule more severely. For example, he might face a villain who was directly or indirectly responsible for Aunt May's death and be on the verge of crossing that line.
Peter Parker's character development can be shown through his emotional journey. He may become more withdrawn at first, but then gradually find strength within himself to move forward. For instance, he might start to focus more on helping the less fortunate in Aunt May's memory.
Peter might initially be in a state of shock. He could isolate himself from his friends and the world around him, constantly replaying memories of Aunt May in his head. He may also feel a great sense of guilt, thinking that he could have done more to protect her.
Writing such 'fanfic' involving sexual content about a character like Aunt May is completely inappropriate. It violates the respect and integrity of the character and is not suitable for public or private creation in a moral and ethical sense.
One plot twist could be that Aunt May's death was part of a bigger plan by a villain. Maybe the villain wanted to break Peter and make him more vulnerable. Another could be that Aunt May left behind a secret that changes Peter's view of his family or his powers.
The negative impacts are numerous. Firstly, it goes against the family - friendly nature that Aunt May often represents in the original works. Secondly, it can create an uncomfortable environment for other fans, especially younger ones who might be exposed to it. It also degrades the overall perception of the fan community as it involves inappropriate and disrespectful content.
Well, it might have Aunt May secretly collecting Doc Ock's memorabilia. Maybe she has a hidden stash of newspaper clippings about his schemes or a small model of his mechanical arms.
Peter might be initially very nervous. He's been keeping this huge secret from Aunt May for a long time, and now that it's out, he's worried about how she'll react. He might stutter and struggle to find the right words to explain himself.
He could become more withdrawn.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.
When writing a Spiderman and Aunt May lemon fanfic, start with a solid plot idea. Maybe something like Aunt May discovers Spiderman's secret identity in a very emotional way and that changes their relationship. Then, develop their characters further in this new context. For the lemon aspect, it should be tasteful and not just about physicality. It should be part of the overall emotional journey of the characters. Also, don't forget to proofread and edit your work to make it as polished as possible.