First thing you will need to do is create a criteria as to how to assign the blame for each death.
For example, Nagasaki and Hiroshima, where the deaths from those two incidents religious or secular?
How do you determine that?
I mean, are they Christian because the USA is a Christian nation?
Are they Christian because it was Christians in the plane the dropped the bombs?
What happens if it comes out that half the crew was Christian and Half was atheist?
No doubt that establishing such a criteria would be contentious at best, more likely impossible. When we get down to specifics I have no doubt that we will hear that religion was never to blame. In any case here's a link that gives a nice overview of Christian conquests:
Christian Atrocities | Victims of Christianity | Catholic Church Inquisition | Crusades