How would you sum up in a few words the unacceptable and unnatural control that some countries' leaders and governments impose on their populations?

One word that describes a government that holds total control is a dictatorship.

A dictatorship is a type of authoritarianism, in which politicians regulate nearly every aspect of the public and private behavior of citizens. 

Perhaps the strongest dictatorship that has existed was that of the government of Nazi Germany. Under the dictatorship of Adolf Hitler, religion was controlled--Hitler said that Catholicism was fit only for slaves. Those who were considered inferior, mentally (those considered insane or severely mentally or physically challenged) or racially (i.e. Jews and Gypsies) were exterminated. The T4 Program was a program of forced euthanasia for many in psychiatric hospitals. Concentrations camps were responsible for the deaths of thousands.
Selective breeding also was encouraged.

The aim was the creation of the "Volk," a nation or people made up of the most superior of the human races.

Hitler hoped for a united German identity founded upon a superior race and total state leadership. 
Children were indoctrinated under Nazism. They were drilled in ideology from a young age. They marched and recited the creeds of the regime wearing swastikas on their arms.
http://www.duhaime.org/LegalDictionary/N/Nazism.aspx

https://www.reference.com/world-view/dictatorship-d72856592e963f3d