Pol Pot

The Doctor had met Pol Pot sometime during or prior to his third incarnation. (COMIC: The Heralds of Destruction) The Eighth Doctor said that he would rather spend time in the company of Pol Pot than with Morella Wendigo. (AUDIO: Nevermore)

In the Unbound Universe, the Master recalled Pol Pot ordering the execution of every doctor he could find, as one of his many schemes to attract the Doctor's attention so he could escape Earth. (AUDIO: Sympathy for the Devil)