I really like the fanfic 'The Meeting of Ice and Night'. It starts with an unexpected encounter between Pitch and Jack Frost. The author does an amazing job of building the tension as they interact, and it shows how their powers could potentially clash or complement each other in different situations.
One great Pitch x Jack Frost fanfic is 'Frost and Darkness'. It beautifully explores the dynamic between the two characters, with Pitch being intrigued by Jack's carefree nature while Jack is drawn to Pitch's mystery. The story has some really well - written dialogue that brings out their personalities.
There's also 'A Bond Beyond Seasons' which delves deep into a possible friendship or more between Pitch and Jack. It shows Jack trying to understand Pitch's motives better and Pitch gradually warming up to Jack. It's a long - form fanfic that has a lot of character development and interesting plot twists.