In the fanfiction, the setting could be during the height of the First Wizarding War. James is on a mission for the Order of the Phoenix, and Snape, who is deep undercover with the Death Eaters, sees James as a target. Snape could use his knowledge of James' habits and weaknesses, learned from their school days, to set a trap and ultimately kill him. This would add an element of espionage and betrayal to the story.
One way could be to explore Snape's long - held grudges against James. Maybe start with a flashback of all the bullying James did to Snape at Hogwarts. Then, set a scenario where Snape is pushed to the limit, perhaps by James endangering Lily. Snape, in a moment of rage and self - preservation (mentally of Lily), uses a powerful spell on James.
One possibility is that Snape has a change of heart. Maybe he realizes that despite their differences, James is a father and a valuable member of the wizarding world. In some fanfictions, Snape might be in a situation where he sees James being wrongly accused, and his sense of justice kicks in to save him.
A fanfiction of their fight could be really intense. James could be motivated by his jealousy towards Snape's closeness with Lily. He might want to show off in front of her. Snape, who has a deep - seated dislike for James due to his bullying, would be more than ready to engage. Their fight could range all over the Hogwarts grounds, from the corridors to the Forbidden Forest. Spells would be flying everywhere, and other students might get caught in the crossfire. It would be a chaotic and exciting scenario to read about.
One reason could be that James finally realizes the extent of his bullying. In the original story, James often harassed Snape. In fanfiction, he might come to understand how much pain he caused Snape and feel genuine remorse. Another reason could be that he discovers new information about Snape that makes him see Snape in a different light. For example, he might find out about Snape's love for Lily and how his actions towards Snape affected Lily as well.
Snape's view of James might not change much at first. He has such deep - seated hatred for James due to their past. But if the fanfiction shows James in a more positive or sympathetic light, he may start to question his long - held beliefs about him, just a little bit.
One possibility could be that there was some sort of magical interference. Maybe a powerful magical artifact or a spell was in place that deflected the Killing Curse just enough for James to survive. For example, if there was a hidden protection charm on him that he wasn't aware of.
Often, James is shown as either the bully he was in the books or as a more nuanced character who has grown past his school - day flaws. Fanfiction can give him a chance to redeem himself in Snape's eyes. Snape, on the other hand, is usually portrayed as the long - suffering victim of James' bullying, but also as a complex character with his own motives and secrets.
One possible plotline could be that Snape discovers a hidden weakness of Voldemort. Maybe through his years of spying, he finds out that a certain spell, when combined with an ancient magic artifact, can destroy Voldemort. So he devises a plan to get hold of the artifact and uses the spell at a crucial moment when Voldemort is off - guard, perhaps during a major battle when Voldemort is focused on other opponents.
One possible motive could be a conflict over their loyalties. Remus is a werewolf and has his own set of insecurities and allegiances. Maybe Snape discovers something about Remus that he threatens to expose, leading Remus to kill him in a moment of panic. For example, if Snape were to find out about Remus endangering students during his werewolf transformations and was about to report him to the authorities.
A great fanfiction is 'Cursed Bonds'. Here, Snape's curses on James are not just simple spells but are tied to a deeper, more mystical bond between them. The story unfolds with a series of adventures as they both try to break or understand this bond that the curses have created.
In most cases, it's not ethical. Torture is a cruel act. However, in the context of fanfiction, some might argue it depends on the overall narrative and the 'rules' set within that fictional universe. If it's part of a revenge plot where Snape has been deeply wronged by James in the past, it could be seen as a morally gray area. But generally, torture is not a positive or ethical behavior.