Dexter Morgan

Title character and main protagonist of the Dexter (Tv Series) books and TV series, played by Michael C. Hall in the latter and Patrick Gibson in the prequel series Original Sin. In both mediums, Dexter is a forensic blood splatter analyst who moonlights as a serial vigilante killer to curb his homicidal impulses (which he refers to as his "Dark Passenger") without violating his code of ethics or being caught.