With her life at an end, Olenna finally ‘fessed up that she was the one who orchestrated the death of Joffrey back in Season 4.
Olenna’s final (and awesome) request was that Jaime tell Cersei so that she would know it was Olenna–not Sansa or Tyrion or anybody else–who had pulled off the murder of the king at his wedding.
Season 7 of Game of Thrones featured the death of one of the most entertaining characters ever to appear on the show, as Olenna Tyrell chose to drink poison courtesy of Jaime Lannister rather than face what could have been a brutal execution courtesy of Cersei.