In the long run, Batman might try to atone for his actions. He could become more withdrawn or even more brutal in his fight against crime, believing that he has already crossed the line so there's no going back. Or he could strive to find a new moral compass and a way to make up for what he has done, perhaps by trying to reform some of the villains instead of just fighting them.
The Joker's death at Batman's hands could also have an impact on the other villains. Some might see it as a warning and become more cautious, while others might see it as an opportunity to fill the power vacuum left by the Joker. Harley Quinn, for example, could either be driven to seek revenge on Batman or be forced to reevaluate her own life of crime without the Joker's influence.
A fanfic where Batman kills Joker could be very complex. For instance, the Joker may have planned his own death in a way that would make Batman cross the line, in order to prove that everyone can be corrupted. Batman's killing of Joker could then send shockwaves through the criminal underworld and among the other heroes. Some may see it as a necessary evil, while others may view Batman as having become a murderer, leading to a great divide in the DC universe of the fanfic.
One common theme is chaos. With Batman gone, Gotham descends into utter chaos as the Joker runs amok. Another theme is revenge. Sometimes the story is about someone seeking revenge for Batman's death. Also, the exploration of the Joker's victory is a theme, showing how he relishes in finally killing his nemesis.
Often, there's a theme of justice being redefined. When Batman kills the Joker, it questions the traditional forms of justice in Gotham. It might also explore the theme of power. Does Batman become more of a tyrant or does he find a new way to use his power for good? And there could be a theme of redemption for Batman, as he tries to justify his actions to himself and others.
He could also develop relationships with other characters in new ways. Maybe he forms an unlikely friendship with a Batman - like figure who sees the good in him and tries to help him break free from the Joker's shadow. Or he could have a falling out with his friends from the Danny Phantom world who are scared of his newfound connection to such a dangerous villain.
There are some out there. Some explore the dark and twisted nature of such a scenario, delving into the psychological impact on Gotham and the other characters. However, the quality can vary greatly. Some might focus more on shock value while others try to build a complex narrative around it.
For Marinette, she might become more serious and less impulsive. Growing up under Batman's guidance, she would learn to think more like a detective and strategist. For Batman, he could become more open - minded. Marinette's positive attitude and creativity could break through his usual stoicism.
Sarada may initially be in awe of Sakura's strength and skills, but as the story progresses, she could start to see Sakura as a normal person with her own flaws. This realization could make Sarada more relatable and human. Sakura could develop a more nurturing side as she helps Sarada through tough times. They could also both develop a stronger sense of family and loyalty towards each other, which could be tested during difficult situations in the fanfic, like when the village is in danger and they have to make tough decisions.
Konohamaru could develop his skills in areas other than combat, like learning about the importance of medical knowledge from Sakura. This would make him a more well - rounded ninja. Sakura, on the other hand, might become more confident in her leadership abilities. By guiding Konohamaru, she realizes she has the potential to lead others in the ninja world.
For Ashfur, he could develop from a jealous and vengeful character to a more understanding and selfless one. Maybe he realizes that his love for Squirrelflight was more about possession than true love, and he starts to focus on the well - being of the clan instead. For Squirrelflight, she might become more empathetic towards Ashfur as she sees him struggle with his emotions. She could also grow in her leadership skills as she has to deal with the situation involving Ashfur.
For Hermione, she might develop a more empathetic side towards Snape. She could start to understand his past traumas and the reasons behind his cold exterior. This could make her less judgmental and more open - minded. As for Snape, he could soften up. With Hermione's influence, he might show his more vulnerable side and let go of some of his grudges, especially towards the students he disliked at Hogwarts.