A medieval Earth executioner
An executioner was an individual who administered the death penalty. An executioner who performed decapitation was called a headsman.
Governor Kodos was dubbed "Kodos the Executioner" after ordering the deaths of 4000 residents of the Earth colony on Tarsus IV. (TOS: "The Conscience of the King")
In 2364, Karnas reminded Mark Jameson of the efficiency of his executioners, which the latter had seen before. (TNG: "Too Short A Season")
In 2370, when about to kill The Albino, Kang told him to look upon his executioners. (DS9: "Blood Oath")
In 2372, young Kar told Chakotay that he was not his son, but his executioner. (VOY: "Initiations")
Also that year, Kathryn Janeway told Mabus that the USS Voyager would not survive by making deals with executioners. (VOY: "Alliances")