8. Travis Marshall - The Doomsday Killer - Season 6
Season 6 aimed to go back to the show's roots by focusing on a single "big bad," this time being the Doomsday Killer, Travis Marshall. We're led to believe for the majority of the season that Travis is aided by his mentor, Professor James Geller (played by the always awesome Edward James Olmos), though it's revealed that Geller is actually dead. Travis killed him before the season began, and we've only been seeing the hallucination of him that Travis sees. Geller is, ultimately, a physical manifestation of Travis' own Dark Passenger. The Doomsday Killings remain some of the most unique, and graphic, of the entire show. His ritualistic killings recreated images from apocalyptic stories in the Bible, including the Four Horses of the Apocalypse and the Whore of Babylon. He even tries sacrificing Dexter's son, Harrison, which he thinks will mark the beginning of a new world. Dexter stops Travis in time, and brings him back to his church to kill him. For some reason, Marshall doesn't get much love from fans of the show, and is often regarded as one of the worst antagonists. Personally, I thought he was quite interesting, and the reveal that Geller had been dead the whole time was one of the best handled twists in the show. He also has had one of the longest lasting effects on Dexter, since killing Travis led to Deb's discovery of his secret.
Memorable Moment: Killing his own sister and displaying her as The Whore of Babylon at the school where she worked.