http://en.wikipedia.org/wiki/Soviet_genocide Entire nations have been collectively punished by the Soviet Government for alleged collaboration with the enemy during World War II. In legal terms, the word "genocide" may be appropriate because specific ethnic groups were targeted. At least nine of distinct ethnic- linguistic sub-nations, including ethnic Germans, ethnic Greeks, ethnic Poles, Crimean Tatars, Balkars, Chechens, and Kalmyks, have been deported to remote unpopulated areas of Siberia and Kazakhstan. It is commonly accepted that the ethnicity-targeted population transfers in the Soviet Union led to millions of deaths due to inflicted hardships. Koreans and Romanians were also deported. Mass operations of the NKVD were needed to deport hundreds of thousands of people.
The deaths of millions of people in Ukraine during the Holodomor famine of 1932-1933 was, according to many historians, caused intentionally by confiscating all food and blocking the migration of starving population by the Soviet government. The number of Golodomor victims was estimated by Robert Conquest as 5 million [11] Overall number of peasants who died in 1930-1937 from hunger and repressions during collectivisation (including Kavkaz and Kazakhstan) was at least 14.5 million [11]. More than a million of people died earlier during other famines in Russia and USSR.
By the way, somewhere around 20 million of the deaths in WWII were Soviet soldiers simply mowed down in battle because of poor preparation or lack of arms or clothing. This does not include the prisoners of war which the Germans killed.
A significant amount of research has demonstrated that there are two solid preventive factors to genocide: democratic government and economic wellbeing. While these are very complicated factors, it is a simple thing to pursue. I will discuss this at the last, how you can promote a genocide-free world, particularly by supporting these two goals.