12. Ray Speltzer - Season 7
Ray appears around the same time that Deb learns that Dexter is a serial killer. He is only present for a couple of episodes, but his impact on Deb and Dex's relationship was big enough to land him a spot on this list. Ray is a psychotic serial killer who lures female victims to his home, then murders them in a grotesque yet unique ritual while wearing a bull horned helmet. He is extremely violent, releases his victims into a handmade maze, then stalks and brutally beats them to death with his bare hands before ripping the earrings off of their corpses to keep as trophies. At this point in their relationship, Debra refuses to accept what Dexter does, even if Harry's code keeps him from killing innocent people. He offers Speltzer as a way to show Debra that he's doing society a favor. At one point, Speltzer catches Dexter and knocks him out before placing him in the maze. Dexter escapes, and Deb later confesses that she wanted to kill Speltzer and that he's a prime example of the flaws in the system. Dexter then tracks down and kills Speltzer, and when he confesses to Deb what he did, she tells him she's glad. It's the first time Deb is actively involved in one of Dexter's kills, and the way she grapples with feeling glad about Dexter killing him shows that she may not think of the world as strictly black and white anymore.