Gangus Khan - The Mongol Conqueror

Gangus khan and his descendants killed a lot of people upwards of about 60 million or so. He wiped out ancient cities like merve, one of the biggest cities in the mediaeval world. The population of iron was something like ten % of its total population once he and his armies were done,. nd it didn't recover till the twentieth century. And then destroyed nac humans, but infa structure too. So i don't just have to rely on historical documents. I can also rely on ecology to prove how bad gengus and his descendants were. They caused the only known case of man made trigger global coolie.