#5 Genghis Khan
Temujin, which was his real name, put under his control most of the Mongolian tribes in the northeast Asia and pronounced the Mongol Empire, with him being Genghis Khan (emperor). He established a military state and managed to conquer most of the Eurasia. He was a brilliant battle tactician and military commander but is also known for leaving massacres in any city he went through. In the Iranian Plateau he killed two-thirds of the population (around 10 million people), he annihilated all major Eastern Europe cities, and sacking of Urgench might be known as one of the bloodiest massacres in our history. It is said that over 1 million civilians died in just one day.