In some fanfictions, it could be related to a power struggle within the wizarding world. If Hermione was seen as a threat to Ginny's family or her own standing in the magical community, Ginny could be pushed to the edge. Also, if there was a rift in their friendship over ideological differences, like Hermione's more logical and rule - based approach clashing with Ginny's more impulsive and instinctive nature in a very extreme way, it might lead to such a tragic outcome.
In some fanfictions, it might be due to a broken relationship. For example, if something goes terribly wrong between her and Ron or Harry, she could sink into a deep depression and see no way out. She may feel that she has lost the most important people in her life and can't bear the emotional pain.
It could also be that the situation was extremely dire. For example, the troll was about to destroy something very important, like a magical artifact that could cause great harm if it fell into the wrong hands, and Hermione saw killing the troll as the only way to prevent that.
The idea of subverting the expected relationships is appealing. Instead of the more common pairings, this pairing offers a fresh take. It also allows for a deeper exploration of the characters' personalities. Since they are so different, seeing them come together in a romantic way can be really interesting for fans who want to see new aspects of their favorite characters.
One reason could be pure hatred. Bellatrix despises Muggle - borns, and Hermione being a very intelligent and powerful Muggle - born would be a prime target for her wrath. Another could be jealousy. Hermione's skills and knowledge might make Bellatrix feel inferior, leading her to lash out.
One possible reason could be jealousy. Maybe Ginny is jealous of Hermione's intelligence or her close relationship with Harry. So, out of spite, she uses the slur.
Well, perhaps in the fanfiction, Harry might feel that Hermione understands him on a more profound level when it comes to his role as the Boy Who Lived and his struggles with the wizarding world's future. Ginny, while she loves Harry, might not be as involved in those complex aspects. Also, the author might write it so that Hermione and Harry have a shared vision for the future of the wizarding community that Ginny doesn't share, leading Harry to choose Hermione.
One possible reason could be the strong intellectual bond Harry has with Hermione. They've been through so many adventures together, solving mysteries and facing challenges. Their shared love for knowledge and learning might make Harry realize he has a deeper connection with Hermione compared to Ginny.
There might be such fanfictions out there, but this is a rather dark and unorthodox concept within the Harry Potter fandom. Most fanfictions tend to focus on positive relationships and adventures rather than such extreme and negative scenarios. However, it's possible that some edgy or AU (alternate universe) fanfictions could explore this idea in a more thought - provoking or symbolic way rather than being purely about violence.
One possible reason could be a misdirected spell during a battle. In the heat of a fight, Harry's spell could go awry and accidentally kill Malfoy. Another reason might be if Malfoy was under the control of a dark wizard and was about to do something truly terrible, and Harry had to stop him at all costs, including taking his life.
Well, it could be a culmination of events. Uther's growing distrust of those around him, combined with Merlin's secretive nature about his magic. Merlin might be caught in the middle of a power struggle or a plot against Uther, and Uther, in his quest to protect his throne and Camelot, decides to eliminate Merlin without fully understanding the consequences. This would also create a great deal of drama and conflict for the other characters in the story, which is something fanfiction writers often strive for.