For civilian deaths caused by the government, I found these statistics, which are only for the 20th century:
- China: 1949–1987 - the communist party killed 76,702,000 people
- USSR: 1917–1987 - the communist party killed 61,910,000 people
- Combined western colonialism: killed 50,000,000 people
- Germany under Hitler: 1933–1945 killed 20,946,000 people
- Japan: 1936–1945 killed 5,964,000 people
From here: What country has killed the most civilians? - Quora
cite given is healthresearchfunding.org (I didn’t check their cite).
Slavery wasn’t the murder and torture fest that some folks make it out to be. Slaves were basically farm animals. How many farmers go out and routinely torture their cows? You don’t do that sort of thing if you want your cows, or your slaves, to be productive. The deaths from slavery mostly come from transporting the slaves across the Atlantic, or from raids and wars related to slavery. Depending on whose numbers you use, somewhere between 1 and 2 million total people died related to slavery, which is definitely not a small number, but it’s not terribly significant when totaled in with other deaths.
Most Americans (including me until I was long out of high school history classes) have a very distorted view of WWII. We think of it as mainly the Germans against everyone else. Sure there was this other front where the Russians were doing stuff, but the U.S. basically came in and saved the day. Russians tend to have the exact opposite view, that the war was mostly Russia against Germany, with this tiny little almost insignificant bit over on the other side. If you really look into it, and especially if you look at the numbers, the Russian viewpoint is actually probably closer to the truth.
Russians killed a staggering number of Germans in WWII. In the battle of Stalingrad alone, Germany lost roughly half a million soldiers. To put that in perspective that’s roughly the same number of soldiers that Germany lost to all of the Allies in total throughout all of WWII. It’s also roughly the same number of soldiers that the U.S. lost total in WWII. And Stalingrad was just one battle. In total, over 4 million Germans died fighting the Russians. But, as huge as that number is, it’s not the number one slot, not even close. While exact numbers are disputed among various sources, the total military deaths for Russia are somewhere between 10 and 20 million, and the total civilian deaths are also estimated to be somewhere between 10 and 20 million.
Deaths caused by the U.S. are almost insignificant in these staggeringly horrible totals.
As for indigenous people, there doesn’t seem to be any good estimate for the population of what is now the U.S. from back in the 1500s. Estimates range from 2 to 10 million. Overall, estimates are that the population of all indigenous people in the western hemisphere was reduced by somewhere between 80 to 95 percent between 1500 and 1700. This includes deaths by smallpox and other diseases and other factors such as scarce resources that would limit population growth or actually cause population decline without necessarily killing anyone. While the U.S. certainly isn’t innocent regarding indigenous deaths, Spain is probably responsible for significantly more deaths simply because there were a lot of Aztecs before Spain came along. Since the Aztec empire was so large, it had the greatest total deaths, even if the percentages were all in the 80 to 95 percent range all through the western hemisphere.
The U.S. definitely isn’t #1. Not even close.
By the way, if you haven’t seen this about WWII, watch it. It’s very good at putting all of the deaths into perspective: