- Severe
- In Season 6, Dexter and the forensics team investigate a serial killer who believes that he has been chosen by God to rid the world of sinners.
- Season 6: With a crazy religious Christian named Travis who tries to end the world. The scenes are often in a dark church in a very creepy setting. At the end of the season there is a scene where Travis almost kills a small baby which is very disturbing.
- (Season 1)Throughout this season, Dexter is taunted by a serial killer, named the Ice Truck killer, who seems to know his real identity. He later finds out that the Ice Truck killer is his long lost brother. He does not remember him because his memory is suppressed due to the trauma of witnessing his mother being murdered. His brother wants Dexter to kill their foster sister. Dexter refuses and kills his brother instead.
- In Season 4, Dexter becomes obsessed with finding the trinity killer who has been committing murders in a fixed pattern in various states all over America in the past few years. Firstly, he kills a woman in a bathtub, then he forces a woman, who is a mother of two, to jump to her death, ending with the brutal beating of a man that leads to death. Dexter manages to trace the identity of the trinity killer and is surprised that he has a family and that he keeps up a good front. He decides to delay killing him as he thinks he can learn something from him. However, his delay in killing him costs him a great price.
- In Season 5, Dexter, who is devastated after Rita's murder, manages to get a nanny to look after his baby son while his two step-children goes to live with their maternal grandparents. While on leave, he turns his attention to killing a serial killer, Boyd Fowler, but his act is witnessed by one of the victims of the serial killer, Lumen. Later, Dexter manages to convince her that he will not harm her and learns from Lumen that besides Boyd, there were other men who raped her too. They became partners in crime, tracking down the men and killing them. In the process, Dexter and Lumen fall in love, but she leaves him eventually once she had avenged the men who raped her.