1. Genghis Khan
Often regarded as the greatest conqueror of all time, Genghis Khan's invasions often included large-scale massacres of the civilian populations. As a result, his bloody invasions have a fearsome reputation in history.
Whenever Qin Shi Huang captured people from other countries, he castrated them and made them his slaves. He also killed several scholars who disagreed with his ideas and ordered the burning of many important books.
After Vlad the Impaler's death, many books describing his cruel acts became bestsellers in the German-speaking territories. It is said that he strengthened the central government with the aid of brutal punishments. His reputation for cruelty inspired the name of the popular character 'Count Dracula' as he was also known as Vlad Dracula.
Ivan the Terrible was prone to episodic outbreaks of mental instability, paranoia, and rages. The later years of his reign were marked by the massacre of Novgorod, an infamous attack launched by him on the city of Novgorod, Russia.
5. Timur
It is said that Timur's military campaigns wiped out 17 million people, about five per cent of the world population at the time. Hence, his armies were feared throughout Africa, Europe, and Asia.