Maybe it takes place in an alternate universe where the world is a bit different. Batman is more open with his emotions. He takes Wonder Woman to a special place, like an ancient, hidden garden. There, he tells her how much she means to him, not just as a teammate but as someone he has romantic feelings for. He might talk about how her strength and beauty have always attracted him, and how he has been trying to hide these feelings for a long time but can't anymore.
One possible scenario could be that they are in the middle of a life - or - death battle against a common enemy. In the heat of the moment, as they realize how much they rely on each other, they share a kiss. It could be a moment of pure instinct and connection.
One possible plotline could be that Batman confesses his love for Wonder Woman during a dangerous mission. They're in a tight spot, and he realizes he might not get another chance. So he blurts it out, adding a whole new layer of tension to their already complex relationship as superheroes.
One possible plotline could be that Batman sacrifices himself to save Wonder Woman from a powerful enemy. Maybe he takes on a self - destructing device or holds off a horde of villains while she escapes. Another could be that he is poisoned by a new and deadly toxin, and in his final moments, he imparts some crucial knowledge or advice to Wonder Woman.
The confession could also lead to new team - ups. Maybe they start to work together more closely on missions, combining Batman's detective skills with Wonder Woman's combat and diplomatic abilities. This could result in a more efficient way of handling threats in the DC Universe. It could also open up new storylines where they have to face enemies who target their relationship specifically.
One possible storyline could be that they are facing an extremely powerful and ancient evil. This evil has the power to corrupt the very essence of the world. Batman and Wonder Woman, in their attempt to stop it, find themselves in a situation where they have to sacrifice their lives. Maybe they are lured into a trap where the only way to prevent the evil from spreading across the universe is for them to use their combined powers in a self - destructive way.
One possible plot could be that Wonder Woman is under the influence of some sort of mind - control. Maybe a villain has taken over her mind, and she attacks Batman, who is initially confused as to why his ally has turned on him. Another plot could be a difference in their views on how to handle a major threat in Gotham or the DC universe as a whole. Their conflicting approaches lead to a physical altercation where Wonder Woman accidentally hurts Batman.
In some fanfictions, a new super - powerful villain might be introduced who has unique abilities that give them an edge over Wonder Woman. This villain could use their powers to outwit and physically overpower her.
A possible storyline could be that Wonder Woman comes to Gotham to investigate some strange occurrences that seem related to her world. She teams up with Batman, and they discover a cult that is trying to summon an ancient evil. Along the way, they learn to respect each other's methods.
One possible scenario could be in a battle against a powerful new villain. Maybe this villain has some sort of weapon that can penetrate her defenses, like a magic blade. Another could be that she's caught in a trap set by her enemies while trying to protect an innocent. In some fanfictions, she might also get hurt because she's overexerting herself to save a large number of people all at once.
Batman might avoid Wonder Woman in fanfic because he's afraid of getting too close to someone with such strong emotions. He's used to suppressing his own feelings, and Wonder Woman is very passionate. Her presence could stir up emotions in him that he doesn't want to deal with in the fictional stories.