I'm looking to list as many as I can think of. Help me out if you can. This is in no particular order of deviance.
1. The witch hunts and burnings of early colonial America and medieval Europe.
2. Human Sacrifices of Aztecs, Mayans, Toltecs, Olmecs and other New World tribes.
3. Suicide bombings in the middle east.
4. World Trade Center attacks.
5. The crusades of Christendom
6. The crusades of Islam
7. Death warrants for all who wouldn't worship King Nebuchadnezzar's idols.
8. Islamic genocide of Turks on Armenians
9. Christian genocide of Native Americans who wouldn't convert.
10. Al Qaeda
11. The Gadianton Robbers of ancient America
12. The gladiator "games" of the Roman coliseum in honor of their gods.
13. The coerced marriages in the name of religion.(Islam, Christians, Hindus and other religions have been guilty of this.)
14. Infant baptism doctrine of Roman Catholic Church.
15. The Spanish Inquisition.
16. The execution of Jesus and his apostles
17. The execution of Joseph Smith and many other mormons for being blasphemous.
18. Lynchings of the Ku Klux Klan.
Some of these were not really religiously driven -like Ku Klux Klan lynchings. That was actually Democrat politics at its worst. Blacks weren't killed because of their religion (which was also Christian anyway) -but because of their POLITICS. After the Civil War, liberated blacks voted Republican and not Democrat like their former masters which pissed off the loser Democrats who believed they were justified in terrorizing their former slaves as punishment for not remaining loyal to their former masters. Joseph Smith's death was far more related to his own attempts to gain political control and using violence himself to try and do it - than his own religious beliefs. Arranged marriages have existed for most of man's history -but using religion to justify them does NOT account for most of them. Jousting for increased status and political power did -so those done in the name of religious belief hardly count as being worse than those done to improve a family's status and power. And some of these other examples you have were responsible for killing far fewer people than you probably think. For example, while some -typically the anti-Catholic and anti-religious -claim the Spanish Inquisition killed MILLIONS -it didn't. That kind of stupid claim is made by those ignorant about the fact the total population of Europe and Russia combined was less than many of the hokey claims made about the numbers killed. The most credible estimates relying on the best evidence and not sheer prejudice -put the number between 3,000 and 9,000. Over a 600 year period. Being burned in effigy may have counted as good as the real thing during those times and more burning in effigy took place than the real thing in those times -but it isn't as good as the real thing when adding up real deaths.
The Spanish Inquisition: A Historical Revision by Henry Kamen is considered one of the best authoritative sources on this one.
Now would you like to compare those figures with those slaughtered and killed in the name of leftist and left wing political ideology? And we won't need to go trolling ancient history to try and prove my point. No need to go back any further than the last century to figure out which is the TRUE evil and scourge of mankind here. We can start with Lenin and work our way through Stalin, Hitler (and NO, Nazism is not right wing political ideology. One totalitarian state is NOT the political opposite of another one -that is just a disagreement about who is wielding the power of the state -while they all agree in using the force and power of government to control the lives of their citizens. Nazism is LEFT WING ideology as is any form of totalitarianism. ANARCHY -no government control - is right wing political extremism) work our way around to those slaughtered by communist China which continues to rack up its numbers, not forgetting the millions slaughtered by Pol Pot before making an acknowledgment of those slaughtered in the name of left wing political ideology in South America. Left wing extremist political ideology - when it gains real control - typically means government terrorism, deadly purges, gulags, forced labor, fatal deportations, man-made famines, massive numbers of political prisoners, extrajudicial executions, show trials and genocide. Every legitimate attempt to put a number to the massive casualties at the altar of left wing political ideology is estimated between 150,000,000 and 260,000,000. Not so oddly enough, a political ideology that almost always denies the existence of God and has so often tried to actively stamp out religious belief in their populations -even using violence to try and do so. What a record of absolute HORROR with immeasurable agony and misery that can be laid directly at the "altar" of left wing political ideology. That number is nearly all those killed at the hands of their OWN leftist-controlled government. Not exactly in line with their claims that they believe in the use of government force and power to control citizens' lives because they so deeply CARE about the people and think government can take better care of them than they can take care of themselves, huh?
Religion isn't a top contender when it comes to the numbers slaughtered for and by leftist political ideologies - just in a handful of DECADES in the last century alone.