On this subject, I like the year 1227 card!
WWI : 19 000 000 of kills : (1% of the world population)
WWII ; 60 000 000 of dead : (2.5% of the world population)
1227 : Gengis Khan : 40 000 000 of dead : (17% of the world population)
Proportionnaly, the conquests of Gengis Khan, was 7 times more brutal than WWII...
End of times of shit...