Facing the monster football game on NBC, the finale of Dexter on Showtime drew 2.50 million viewers for the 9 PM telecast. That was down a fraction from last season’s finale (2.57 million), which  at the time became the most-watched episode of an original series in Showtime’s history, and up 11% from last week (2.26 million). The series, which was recently renewed for a sixths season, hit a season high two weeks ago with a 2.54 million. Including the 11 PM replay, Dexter averaged 2.9 million viewers last night vs. 3.1 million last year. Overall, Season 5 will rank as the highest-rated season of Dexter to date, averaging more than 5 million viewers per week on TV and on-demand. (Word of caution for those who haven’t seen the finale yet: some comments contain spoilers.)