More than an estimated 23,000 Christians were killed in the persecutions of the Roman Empire. As Russia, China, North Korea et al adopted Marxist doctrines and made Atheism the only acceptable religion of the land, they collectively murdered more than 60 million innocent people in the 20th Century alone.
I would be the first to say that evil people use religion in evil ways. There is no way to justify the Crusades, the Inquisition, the Salem Witch trials, et al. But the carnage in the wake of all of that is at the most a few thousand over hundreds of years. And the vast majority of Christendom is innocent of all that.
And now almost all the on going humanitarian efforts around the world--orphanages, leper colonies/ministries, private homeless shelters, ministry to some of the most desperate and needy of the poor in myriad countries are all created and/or staffed by people of faith. Millions more have been saved, restored, benefitted from the such activities by such benevolence than were ever harmed by the misuse of the JudeoChristian religion.
There are no relief agencies or ongoing humanitarian ministries established and staffed by Atheists.