On the U.S. TV series "Dexter", what is Dexter's Dark Passenger?

On the U.S. TV series "Dexter", Dexter's Dark Passenger is his urge to kill very bad individuals (criminals). Dexter's Dark Passenger (a need to kill) was born during his mother's brutal murder by chainsaw at the hands of Santos Jimenez and two other men. After the killing when he was still a toddler, Dexter was trained by his father, Harry Morgan to focus his urge on other killers and to live by a code. Although Dexter had a preferred modus operandi, he would frequently improvise. He found glee in killing and dismembering his victims. His way of working made the disposal of the bodies easy.

In Season 1, the Dark Passenger was mentioned as a general term for the burden Dexter carried as a result of his childhood trauma. In Season 2, the Dark Passenger was used to refer to an addiction, such as for a drug (it was an inconvenient lie). In the following seasons until the end in Season 8, Dexter felt that his Dark Passenger represented a part of his inhumane side, that the only way he could control it was to channel it, not suppress it, and that notwithstanding the Dark Passenger he (Dexter) had to accept personal responsibility for his actions.

"Dexter" is a TV crime drama mystery series that aired on Showtime from October 2006 to September 2013. Set in Miami, FL, the show centers on Dexter Morgan (Michael C. Hall), a forensic technician specializing in blood analysis for the police. Dexter leads a secret parallel life as a vigilante serial killer, hunting down murderers.