In 1959, Ernesto "Che" Guevara oversaw and/or participated in the execution of 15,000 Cubans without due process and in contravention of the Cuban Constitution which abolished the death penalty in 1940. Cuba's population in 1959 was 6 million, which means that Guevara murdered 1 out of every 400 Cubans. 99% of his victims were adult men (though he also executed women and children on ocassion). In respect to just the male population of the island (3 million), Guevara killed 1 out of every 200 Cuban men. And, mark you, that's how many Cubans were killed in the first year of Castroism. There have now been 48 more though none as bloody as that first one.
If Guevara (or, rather, some Guevara clone) were to unleash his Reign of Terror here, killing in exactly the same proportion, it would cost 750,000 Americans their lives.
As a frame of reference, less than 200 individual rebels were killed in the course of the revolution that brought Fidel Castro and "Che" Guevara to power.
Ten-Part Series on "Che" Guevara's Life to Air on PBS Affiliate "V-Me" TV