Soviet Union under Joseph Stalin: Stalin's rule was characterized by forced collectivization, which resulted in widespread famine and the death of millions of people, particularly during the Ukrainian Holodomor. Stalin's purges led to the imprisonment, execution, or exile of millions, including members of the Communist Party, military officials, intellectuals, and perceived political opponents.

The Great Leap Forward in China: Under Mao Zedong's leadership, the Great Leap Forward aimed to rapidly transform China's economy and society. However, the policies implemented, such as forced collectivization and the backyard steel furnaces, resulted in a disastrous famine, leading to the deaths of an estimated 20 to 45 million people between 1958 and 1962.

Cultural Revolution in China: The Cultural Revolution, initiated by Mao Zedong, aimed to reassert his authority and eliminate perceived enemies within the Communist Party and society. The movement led to widespread political persecution, purges, and violence, resulting in millions of deaths, as well as the destruction of cultural heritage, academic institutions, and economic disruption.

Khmer Rouge in Cambodia: The Khmer Rouge, led by Pol Pot, ruled Cambodia from 1975 to 1979. During their regime, they implemented radical agrarian communism, forcing urban dwellers into rural work camps and carrying out mass executions, torture, and forced labor. It is estimated that between 1.7 to 2.2 million people died as a result of execution, starvation, and disease.

North Korea under Kim Il-sung and Kim Jong-il: The oppressive regime in North Korea has been associated with widespread human rights abuses, political repression, forced labor camps, and the suppression of dissent. The regime's policies have resulted in severe food shortages and famine, leading to the deaths of hundreds of thousands of people.