@Robert Gentel,
Pol Pot probably puts the Serbs to shame, although it was certainly not for want of trying. The difference which is most striking is that the Serbs did not and were not able to export their madness beyond the boundaries of the former Yugoslavia, and Pol Pot was not able to export his madness out of Cambodia. I would say that contemporary
informed opinion ranks Pol Pot with Hitler, and the Khmer Rouge with the NSDAP.
Nevertheless, Germany exported their genocide. The SD followed in the wake of the army wherever it went. Beyond that, the war by itself took literally tens of millions of lives (for which Joe Stalin and the Soviet Communist Party bear a good deal of the responsibility). Nine million Germans dead, as well.
No one matches the scale of Hitler and the NSDAP, as RG points out--and no one else has ever successfully exported such a planned genocide.