These two never actually fight one-on-one in the series. They do, however, face each other briefly in the following ways:
* During the Arrancar invasion: Stark and Shunsui have a brief encounter during the initial Arrancar assault on Karakura Town. Stark, along with several other Espada, is observing the fight between Shunsui and his lieutenant Nanao Ise.
* During the battle at Hueco Mundo: Shunsui and Stark are both involved in the larger battle in Hueco Mundo, but they don't engage in direct combat with each other. They are part of different sides of the conflict, and their paths don't cross in a way that would lead to a duel.
It's worth noting that their respective powers and personalities make them an interesting matchup on paper. Stark is a powerful Espada with the ability to manipulate darkness and a calm, calculating demeanor. Shunsui is a skilled captain known for his clever strategies and playful nature. However, their paths in the story never lead to a direct confrontation.