In the context of the "Star Wars" universe, particularly within the narrative of Star Wars Jedi: Fallen Order and Star Wars Jedi: Survivor, Cal Kestis is a strong Jedi who has been through intense trials. If he were manipulated by Darth Vader and played as an Inquisitor, it would depend on several factors such as the context of the encounter, the abilities and resources each character has at their disposal, and the specifics of the conflict.
As for the character Cereal (assuming this is a typo for "Sear" or another character), it would depend on their abilities and situation as well. If Cal is under the influence of Vader, he might be more vulnerable or conflicted, giving Cereal an opportunity. However, Vader is an incredibly powerful Sith Lord with significant dark side abilities, which would make confronting him dangerous for anyone.
In general, in a theoretical showdown, a well-prepared character might have a chance at defeating Cal or Vader, but it would likely be a tough battle given their strengths and skills in the Force. The outcome would ultimately hinge on the circumstances of the fight and the narrative choices made in that scenario.