The moment Game of Thrones jumped the shark

For me, it was the death of Myrcella in Season 5

The show started off by scattering the families of the various houses around Westeros. It was a slow burn, and the prospect of joyful reunions was always dangled over our heads. But in Season 5 I became a bit skeptical that there would ever be any such payoff. When Jamie and Myrcella were on the boat, I was thinking to myself: how will she die?? An arrow fired from the beach? A shark? Drowning? DOH so it was poison lipstick. It occurred to me that the show had become predictable. The whole deal with this show was that it was totally unpredictable, but that was no longer the case in Season 5. Seasons 6 - 8 were a slide into mediocrity, but the slide started with that moment in Season 5 in my opinion.