Who is the character Santino D'Antonio's sister, Gianna D'Antonio, and how does she fit into the John Wick storyline?

Gianna D'Antonio is a character in the John Wick movie series. She is the sister of Santino D'Antonio, the main antagonist in John Wick: Chapter 2. Gianna is a member of the High Table, a council of powerful crime lords that govern the world of assassins in the John Wick universe.

In John Wick: Chapter 2, Santino D'Antonio calls in a blood oath that John Wick owes him. In order to fulfill this oath, Wick is tasked with assassinating Gianna, who is next in line to take over the family's seat on the High Table. When Wick arrives in Rome to carry out the hit, Gianna offers him a deal - if he helps her commit suicide in a way that looks like she took her own life, she will give him a marker that will erase his debt to her brother. Wick agrees, and after Gianna's death, he is attacked by Santino's men and forced to go on the run once again.

Gianna's character serves to deepen the world-building in the John Wick movies, giving viewers a glimpse into the complex web of relationships and power dynamics that govern the world of assassins. Her role in the story also adds a layer of complexity to John Wick's character, showing that even the most ruthless killer has a code of honor that he is willing to uphold.