The 100 Deadliest Episodes in Human History.
The 100 Worst Wars, Genocides and Dictators in History: 10 Bloodiest
Twentieth Century Atlas - Historical Body Count
But you have to consider the world population at the time and extrapolate that to the current numbers.
Then you will realize how tiny ISIS' prick is ...
The Great Genghis Kahn wiped out 1/10 of the world population -- that is like killing 700 million today.
The scary part is that with nuclear weapons we could do the same, or kill more, in a few days ...