Kokushibo is a powerful demon with so much raw power that pretty much all of the other characters fear him. One on one it’s quite possible that none of the Demon Slayers would be able to match him. He just continues to grow more powerful with each passing moment. Priscilla also has solid sword techniques and even a powered up mode of her own but physically she wouldn’t be able to keep up with the sheer speed or technique of Kokushibo. She would not be able to endure these attacks. Kokushibo wins.