Renly's death was perfect. It's why this show is so amazing. It's not the normal suspenseful build up in the last five minutes, commercial break, re-engage suspense, oh shit he's about to do it, Next Time on Game of Thrones: Does he do it? Find out next week.
Instead Renly is just relaxing early in an episode when no major characters would ever be killed and all of the sudden, he's down.