Where did Arya learn to be an assassin?
Arya Stark
Arya is forced to beg on the streets of Braavos, with her fellow acolyte the Waif arriving daily to attack her. Eventually, Jaqen brings Arya back to the House of Black and White and restores her vision. She is tasked to assassinate an actress named Lady Crane, but Arya has a change of heart at the last minute, instead warning Lady Crane of the attempt on her life. The Waif witnesses this disobedience, and is given permission by Jaqen to kill Arya. Aware that she is now in danger, Arya retrieves her sword Needle from its hiding place and arranges for passage out of Braavos, but is stabbed by the Waif and barely escapes. Lady Crane nurses her back to health, but the Waif reappears, kills Lady Crane and pursues a recovering Arya. Arya leads the Waif to her quarters underneath Braavos and extinguishes the only candle in the room, her experience fighting blind ultimately giving her the advantage and allowing her to kill the Waif. She removes the Waif's face and adds it to the Hall of Faces before telling an impressed Jaqen that she is Arya Stark, and returns to Westeros.