Its Nausea Powder is not too threatening as long as there is an Alchemist with the Remedy ability or several Antidotes in stock. It's much more difficult when Oversouled, since it has access to the powerful Flare spell.
Fiend Tale Edit
A notable Big Bully Cap dreamed of becoming a singer before she died during an attack by Sin. After watching Yuna's concert, Big Bully Cap decided to act on her dream with Barkeep as her voice coach. Eventually, Big Bully Cap holds her private concert, but the Fiends attending died from hearing her sing. Believing she did a good job, Big Bully Cap jumped off the airship to find another venue.