The Second World War has been said to be the deadliest and cruelest war of all time. Over 3% of the 1940 world population died during that war that is an estimate of about 70-80 million people. However, the Soviets had the highest human toll because of the great purge where the Soviets were suspicious of their army officers.
Also, the white Russian fought their own people, who also contributed to the number of the human toll. Most of the death of the Soviet civilians were victims of Nazi genocide, which was a result of lack of readiness for the Nazi forces, and over two million deaths were Russian citizens that were deported to Germany for laborers, and over seven million died of famine and disease.
The Soviet Union, despite being one of the victors of World War II ended up having the highest human toll. In addition to the deaths of all the soldiers and military personnel, there were huge numbers of civilian deaths from various causes which might help to explain the high number of deaths.
Some historians and researchers estimate almost seven and a half million Soviet civilians were victims of Nazi genocide. Over seven million deaths have been attributed to famine and disease in both German occupied and non-occupied regions of Russia. And, over two million deaths happened when Russian citizens were deported to Germany as forced laborers under inhuman conditions.