Paine is fought as a boss in Final Fantasy X-2. When the player has obtained all of the Crimson Spheres they gain access to the Den of Woe where Shuyin's emotions preserved in the pyreflies will overwhelm the party and cause them to attack each other. Paine is the second out of the five opponents faced in the Den, after Rikku.
Paine's only attack is to slice Yuna with her sword. It causes more damage than Rikku's attacks, but with high HP and Defense the player should be able to weather all of her attacks without suffering much damage. The player may want to steal from Paine before defeating her.