10. Known as the "Scourge of God", this ruler reigned for less than twenty years, and is estimated to have been responsible for the deaths of twelve million people.
From Quiz The Best of the Worst
Answer:
Attila the Hun
It is thought that Attila became leader of the Huns in 434 A.D. after he murdered his brother, Bleda. By that time the Hunnic Empire stretched from the Ural River into the Roman Empire. The Byzantine Empire, wealthy and affluent, negotiated a treaty with the Huns and paid them to stay away. The poor, dying, western empire was not so lucky. Even though Attila expanded the empire into other areas, the lure of the supposed riches of Rome called him. Stories vary regarding his death; was it a nosebleed? internal bleeding caused by too much drinking? stabbing by one of his wives? or the fact that Pope Leo I sprinkled him with holy water? Whatever the cause, the Huns ceased to be a problem in the Roman empire after that, but Attila gained the nickname "Scourge of God" because of the pillaging, plundering, destruction, and devastation of whatever was in his path.