One interesting plotline could be that the kiss is a moment of unexpected passion during a battle. Barry and Killer Frost are on opposite sides initially, but the kiss changes their dynamic completely, leading them to question their allegiances.
The relationship could also lead to a transformation in Killer Frost. With Barry's influence, she might start to show more of her human side and less of the cold - hearted Killer Frost. They might start working together more often, and Barry could be teaching her about compassion and love, which in turn strengthens their bond.
I don't recommend seeking out or looking for 'dirty' fanfics as they often violate ethical and community standards. Fanfics should generally be about positive creative interpretations of characters.
Some fanfics might explore their relationship in a more platonic or friendly way. For instance, they could be written about how they help each other grow as heroes. These types of fanfics are more in line with the positive spirit of fan communities.
One great 'Batman and Killer Frost Fanfiction' is 'Frosty Encounters'. It shows an interesting dynamic where Batman tries to understand Killer Frost's motives. The author does a great job of portraying Killer Frost's complex personality.
Killer Frost in Young Justice fanfiction can be a really interesting character. She often brings a sense of mystery and power. In many fanfictions, her backstory is explored more deeply, like her struggle with her powers and how she fits into the Young Justice team dynamic. Sometimes she's portrayed as a more complex anti - hero, which adds a lot of depth to the stories.
In some fanfictions, Killer Frost's power over ice and cold is shown as a contrast to the Avengers' more heat - based powers like Iron Man's repulsors. Her powers are often depicted as very dangerous and sometimes uncontrollable, which adds an interesting dynamic when she's around the Avengers.
Killer Frost is alluring in 'Batman: Assault on Arkham' fanfiction because of her powers. Her ability to control ice makes for some really cool (pun intended) action scenes. Writers can use this to create intense battles or escape scenarios. For instance, she could freeze an entire corridor in Arkham to stop guards from chasing her.