Killing for what you believe in? Nah, that's pretty much the realm of fanatical extremists, of which religion has its greater than fair share.
And to your second edits meaning: I also like to stick to facts, but I was replying to Christians claiming that non-godly people are more evil than godly people by pointing out how nasty they believe God to be.
Estimates of how many citizens were killed in the Soviet Union vary and depend on how you count and what you count https://en.m.wikipedia.org/wiki/Number_of_deaths_in_the_Sovi... 2-6m seems a bad enough number for Internet arguments.
Ww2 killed 60-80m and that was caused by Hitler who was Catholic (although he didn't kill in the name of religion).
Of course other things God supposedly created have killed far more, such as Spanish Flu which killed 500m and The Black Death which killed 30-60% of everyone in Europe.
Guilty as charged!
The conversation was generally about what people do in the name of religion. What god has supposedly done is not really relevant to that...
I don't think all that many non-religious people actually care/object when religious people practice their religion as long as it doesn't infringe on anyone else's rights.
These examples share a huge number of common traits with (fundamentalist) religion.