Governor Arnold Kodos (or Kodos the Executioner) was a 23rd century human male who was the leader of the Federation colony on the planet Tarsus IV in the 2240s, and is generally held responsible for the Tarsus IV Massacre.
In 2246, Tarsus IV was used as a test site by the Symmetrists for the Virogen plague. As a result a deadly famine struck the colony, and there was not enough food for the 8,000 colonists. Kodos staged a coup, then declared martial law in which he ordered that 4,000 colonists be killed, so that there would be enough food for the rest of the colony to last until Starfleet aid arrived. The order was carried out, just as a relief task force led by the USS Enterprise reached the colony. (TOS episode & Star Trek 1 novelization: The Conscience of the King, TOS - Enterprise Logs short story: "Though Hell Should Bar the Way", and TOS novels: Avenger, Academy: Collision Course; ENT episode: "In a Mirror, Darkly"; Last Unicorn RPG module: All Our Yesterdays: The Time Travel Sourcebook; TOS reference: The Autobiography of James T. Kirk)
Realizing that his life was in danger, Kodos turned to the Symmetrists who provided him with the identity of Anton Karidian and got him off the planet. A body was later recovered, burned beyond recognition, at Kodos' home, and it was believed to be the body of Kodos. Kodos lived as Anton Karidian until 2266, when he was exposed by Captain James T. Kirk, one of the few remaining survivors that could identify him. (TOS episode: "The Conscience of the King", TOS novel: A Flag Full of Stars)