'Game of Thrones' series finale is the worst-rated episode in the show's history on IMDb. It's also the second worst-reviewed episode in the show's history on Rotten Tomatoes. On IMDb, the worst rated episode prior to season eight was season five's 'Unbowed, Unbent, Unbroken'. Meanwhile, the worst rated episode on Rotten Tomatoes is the fifth episode of season 8.