Skorpios

 was a businessman who wanted to destroy the planet Earth in order to develop the area for commercialisation. He knew of the Fourth Doctor and threatened to kill him to testifying against him. He sent the Children of Pyxis after the Doctor to assassinate him, knowing that knowing people wouldn't remember the attack. He used to kill people himself and kept them as statues. He sent assassins after Romana II after she broke into his house. His original case of causing genocide of a planet by destroying an ecosystem was delayed but he was charged guilty, but escaped a verdict landing in the Witness Protection Universe. He was killed by the Children of Pyxis. (AUDIO: The Doomsday Contract)