There's no way to find out. We've been killing each other since the beginning of times. So you have to go back to prehistoric times to cover many thousand years of wars that were never registered. Then go through all those registered by history, adjust the numbers because they're not accurate and add all the wars not registered historically for one reason or another.

Then check all the records of recent history and make some adjustments because the numbers are not accurate either. Armies are more likely to have accurate records than remote village administrations. WWII surely killed millions of civilians that were not registered anywhere. Add to that people killed in wars in Africa, Middle East and Far East. Places where you can vanish a whole community and nobody is going to find out, at least for a long while. Like in the times of the colonization of America. Who knows the numbers?

And double the numbers for the "official" estimates. Nobody is telling the real numbers. You'll never know for sure how big is the collateral damage of the war in Iraq.

Plus, people dying from the consequences of the wars. Injuries, contamination, abandoned ordinance exploding decades later, economies devastated, etc, etc.

As I said before, we've been killing each other since the beginning of times. I'm sure there's a number that answers your question and it's a huge, very huge, one.