Which brings us to Cersei, who blew up the Sept of Baelor while Margaery Tyrell, the High Sparrow, and dozens of others were inside.
Cersei had her accomplice and advisor, Qyburn, use caches of wildfire to blow up the Sept of Baelor at an opportune time.
The murder victims included: Margaery and Loras Tyrell along with their father Mace, Kevan Lannister (Cersei's uncle), the High Sparrow, Lancel Lannister (Cersei's cousin-turned-sparrow), and dozens of King's Landing citizens and the High Sparrow's followers.