Question: arya who has she killed?
Answer: She slits Lord Walder's throat, getting revenge for his betrayal and murder of her brother, Robb Stark, and her mother, Catelyn Stark. After taking out Lothar Frey and “Black” Walder Rivers, then finishing off Lord Walder Frey himself, Arya used her face-changing powers to set a trap that annihilated House Frey.