Gianna D'Antonio was the former leader of the Camorra crime organization and a member of the High Table, a council of crime bosses. She was also the sister of Italian crime lord Santino D'Antonio, and the employer and close friend of Cassian.
Gianna serves as a pivotal antagonist in John Wick: Chapter 2, where her brother tasks protagonist John Wick with her assassination. Her death leads to a chain of events that turn Santino into a member of the High Table, and his conflict with Wick.
Not much is known about Gianna's early life. At some point in her adulthood, her father gave her the position of leading the Camorra, leaving her brother Santino jealous of this and eventually plotting to kill her to take her place.
While attending a party, Gianna meets Akoni, who confronts her over the fact that she had forced several crime lords to give up their land to her by holding a knife to their throats. Gianna retorts by saying that she had instead held the knife up to their children, and that they are only supposed to watch.
Gianna later goes to put on more makeup. However, she is followed by John Wick, who had been tasked by Santino with assassinating her. Gianna talks with John and asks him who had sent him. John informs her that her brother had made him kill her with the blood oath he had sworn to him.
Resigned to the fact she was going to die, Gianna opts to die her way, and slits her wrists while taking a bath. However, John puts a bullet in her skull after she's assumed to have lost consciousness from blood loss. John didn't seem very happy with the job, but he proceeded anyway, knowing much worse consequences will follow.