From Wikipedia on Pol Pot:

He presided over a totalitarian dictatorship,[6] in which his government made urban dwellers move to the countryside to work in collective farms and on forced labour projects. The combined effects of executions, strenuous working conditions, malnutrition and poor medical care caused the deaths of approximately 25 percent of the Cambodian population.[7][8][9][10] In all, an estimated 1 to 3 million people (out of a population of slightly over 8 million) died due to the policies of his four-year premiership.[11][12][13]

I really don't think you can compare Castro to this track record!