You can try fanfiction.net. It has a large collection of fanfics from various fandoms, and there's a good chance you'll find some amy rose shadow fanfic there.
One good amy rose shadow fanfic could be 'The Adventures of Amy and Shadow'. It might involve their adventures in a magical world where they team up to defeat an evil force. In this fanfic, their unique personalities would shine through as they face various challenges together.
One common theme is family. Since there's a baby involved, it often explores how Amy, Shadow, and the baby form a family unit. Another theme could be protection. They usually have to protect the baby from various threats.
A great 'amy rose and shadow baby fanfic' that I've come across is 'The Bond of Amy, Shadow, and Their Baby'. This one really emphasizes the emotional bond between the characters. It starts with Amy and Shadow unexpectedly finding themselves responsible for a baby. As the story progresses, they learn about love, sacrifice, and the true meaning of family. The way the author portrays their struggles and joys makes it a very engaging read.
Even one of her friends like Tails could be the betrayer in a really unexpected plot twist. Maybe Tails is forced to betray her by some external threat. For example, if an enemy captures Tails and threatens to harm him or Sonic if he doesn't give away some important information about Amy Rose or lead her into a trap.
Amy Rose has a deep affection for Sonic, not Shadow. So in the official Sonic lore, there is no such love story between Amy Rose and Shadow. However, if we were to imagine it, perhaps they could meet during a fight against a common enemy. Shadow, initially cold and distant, might be gradually warmed by Amy's persistent kindness and her strong will. And Amy might be attracted to Shadow's mysterious and powerful nature.
A 'amy rose dies fanfic' could be a very sad and dark take on the character. It might explore themes like loss, grief among the other characters who knew Amy Rose. Maybe it's a way for the writer to show how her death could impact the whole story's universe.
One possible challenge could be their different personalities. Amy is outgoing and affectionate while Shadow is more reserved. This could lead to misunderstandings in their communication. Another challenge might be their different goals. Amy is often focused on Sonic or helping others in a more direct way, while Shadow has his own complex motives related to his past. Also, the public perception in the Sonic world could be a problem. Since Amy was known for her love for Sonic, others might be skeptical or even against her relationship with Shadow.
I highly doubt that 'amy rose poop fanfic' is a popular type of fanfic. Most people are more interested in fanfics that focus on positive aspects of the characters like their relationships, adventures, or character development rather than something as unappealing as poop.