I'm going to assume you mean purges in Communist countries
Communism isn't a country or a form of government. It is an economic system based on theft. It is government ownership of markets. It is what the DEMOCRATS want.
in which religion was persecuted. I will have to note that most of those deaths had NOTHING WHATSOEVER to do with atheism per se. Stalin wasn't purging Christians, he was purging EVERYONE.
Stalin belonged to the Church of No God, just as you do. He was not atheist, and neither are you.
Now, I'm certain there have been quite a few religious people targeted in that setting but it would have to be an enormous amount to catch up with religion's track record of murder.
Particularly the Church of No God.
Notably:
* Hitler's Holocaust, the deadliest of the genocides, driven by the Church of No God. 2/3rds of the Jewish population was tortured and killed. Some estimates are 7 million Jews were killed. Another 3.5 million Russian prisoners tortured and killed.
* The Cambodian Genocide, driven by the Church of No God. About 3 million Christians, Buddhists, and Muslim were killed because of their religion.
Organized religions LITERALLY KILLED PEOPLE FOR NOT BELIEVING IN THE SAME RELIGION.
Let's look at some wars:
* WW2, a non-religious war, resulted in 118 million deaths. The most of any war.
* WW1, a non-religious war, resulted in 40 million deaths. This war did not end in a victory. It ended in armistice.
* The Manchu conquest in China, a non-religious war, resulted in 25 million deaths.
* The Taiping rebellion, a non-religious war, resulted in 30 million deaths (and the fall of China to communism).
* The Crusades, a defensive war against Islam and a religious war, resulted in 3 million deaths.
* The Inquisition, a religious war, resulted in less then 8000 deaths, and many of the Tribunals were not carried out by the Catholic Church.
* Jihad, or the continuing religious wars perpetuated by Islamic radicalists, kills about 26,000 a year.
Souces: Encyclopedia of Wars, the Encyclopedia Britannica.