1. Adolf Hitler: The leader of Nazi Germany, responsible for the Holocaust, the systematic extermination of six million Jews, as well as millions of others, including Romani people, disabled individuals, and political dissidents.
2. Joseph Stalin: The leader of the Soviet Union during the 1930s and 1940s, responsible for the death of millions of his own citizens through forced collectivization, purges, and political repression.
3. Mao Zedong: The leader of the Communist Party of China and founder of the People's Republic of China, responsible for the Great Leap Forward, a failed economic policy that resulted in the deaths of millions.
4. Genghis Khan: The founder and first Great Khan of the Mongol Empire, known for his brutal conquests and the destruction of entire cities and civilizations.
5. Pol Pot: The leader of the Khmer Rouge in Cambodia, responsible for the deaths of nearly two million people during his regime's brutal attempt to create a communist utopia.
6. Ivan the Terrible: The Grand Prince of Moscow and the first Tsar of Russia, known for his cruelty and reign of terror, which resulted in the deaths of thousands of people.
7. Emperor Hirohito: The Showa Emperor of Japan during World War II, responsible for the military aggression and atrocities committed by the Japanese Empire, including the Rape of Nanking and the use of chemical and biological weapons.
8. Saddam Hussein: The former President of Iraq, responsible for the brutal oppression of his own people, as well as the invasion of Kuwait and the use of chemical weapons against Iraqi citizens.
9. Osama bin Laden: The founder and leader of the al-Qaeda terrorist organization, responsible for the September 11 attacks on the United States and numerous other terrorist acts.
These are just a few examples of the many historical figures who have caused great suffering and loss of life. It is important to remember and learn from history in order to prevent similar atrocities from occurring in the future.