4. Genghis Khan
Born probably in 1162, he founded the Mongol Empire and was the first Great Khan and Emperor who ruled from 1206 to August 18, 1227.
Not much is known about him, however, unlike others, Genghis Khan was a tactical tyrant. He led brutally and efficiently, killing only those who got in his way. That could mean anyone from an enemy or even his own brother.
His leadership led to the decimation of almost 11% of the world’s population at the time, roughly 40 million lives.