Germany lost 10% of it's population from direct action in WW2.
Not counting the people exterminated. Hard to say the total percentage lost when you add it all up.
There were no wars like that in the medieval period in the western world. Closest that came to it were the Mongolians, but they were unable to get to us to inflict the kinds of losses they inflicted on the East.
Germany was the ground level. Russia eclipsed Germany. China eclipse Russia.
The Khmer Rouge exterminated about 20% of the population in the Cambodian genocide.
Several million Iraqis died as a direct consequence of the American invasion in 2003, terror wave that resulted in the aftermath, and then the rise of ISIS when Obama helped create them.
I could go on and on with this stuff. Population is higher and so are the body counts.