9. Harrison Kills Dexter - Dexter: New Blood
Though it was intended to serve as a more crowd-pleasing ending to Dexter than the original, widely-loathed series finale, Dexter: New Blood ended up pissing off a lot of fans all over again with its shocking final twist.
While many expected the series, per its title, to conclude with Dexter's (Michael C. Hall) son Harrison (Jack Alcott) either joining Dex or succeeding him as the story's new serial killer, New Blood ended instead with son killing father.
Rather than succumb to the same urges that plagued Dexter's life, Harrison pushed back against his father, forcing him to look at all the death he's caused throughout his life.
Dexter ultimately agrees that they'd both be better off with him dead, and so Harrison reluctantly shoots his dad dead.
Dexter's ex Angela (Julia Jones) then tells Harrison to flee while she alters the crime scene to suggest that she killed Dexter in self-defense, and Harrison drives away to parts unknown, seemingly no longer tethered to his father's demons.
Though the finale received rave reviews from many critics for offering up a more concrete and satisfying finale, many fans expressed extreme disappointment at both Dexter's demise and the circumstances through which it came about.
Whichever side you fall down on, though, it was a ballsy-as-hell move to kill Dexter and make it clear that Harrison wasn't haunted by the same urges, in turn slamming the door on the potential for any future series.