Well, one characteristic is the exploration of their contrasting personalities. Superman is often seen as the idealistic and powerful do - gooder, while Batman is the brooding and more strategic vigilante. Fanfictions usually play on these differences.
One great 'batman x nightwing fanfiction' is 'A Bond Beyond the Cape'. It really delves into their complex relationship, showing how Nightwing's growth from being Batman's sidekick has shaped their dynamic. It has some really well - written action scenes and emotional moments that fans of the duo will love.
Well, in this kind of fanfiction, the 'yandere' trait in Superman can completely change the power dynamic in their relationship. Usually, they are both heroes with their own moral compasses. But with Superman being yandere, he might cross some boundaries. For example, he could start making decisions for Batman without his consent, all in the name of 'love' or 'protection'. And Batman, being the independent and brooding character he is, would surely struggle against this new Superman, which would make for a great story of conflict and resolution.
One great 'Batman x Robin Fanfiction' is 'The Dynamic Duo's New Adventure'. It really captures the essence of their relationship, with Batman being the brooding mentor and Robin the eager protege. The story takes them on a journey through Gotham's underbelly, facing new villains and challenges that test their bond.
One idea could be that Batman discovers the reader is pregnant and he struggles with how to protect both her and the unborn child while still fighting crime in Gotham. He might become even more vigilant and start to plan for a safer future for his new family.
One great 'Batman x Riddler Fanfiction' is 'The Riddler's Redemption'. It shows an interesting take on the Riddler trying to turn over a new leaf and his complex relationship with Batman during that process.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfictions, and there are quite a few 'Batman x Riddler' ones. Just use the search function and type in the relevant tags.
I would recommend 'Batman's Unlikely Ally'. In this fanfic, the reader is a normal citizen who unexpectedly becomes important to Batman's fight against crime. It's filled with action scenes and some really sweet moments between the two characters. The way the author describes the relationship development is quite interesting.
Alfred would be a great addition. He could offer his wisdom and support to Batman and Batgirl's relationship, and also provide some much - needed comic relief. Another good character is Commissioner Gordon. His connection to the Bat - family and the police force could add an interesting dynamic to the story, especially if he has to deal with the relationship between Batman and Batgirl in some way.
One possible fanfiction could be that the Joker, after years of chaos, finally realizes that his true purpose was always to be in Batman's life. In a moment of self - discovery, he approaches Batman not as an enemy but as someone who needs him. Batman, initially skeptical, begins to see that the Joker's madness is a mirror to his own dark side. They start to form an unlikely bond where they complete each other in understanding the fine line between order and chaos.