1. Communism
👉 65–100+ million

2. European colonial empires
👉 30–60+ million (Americas, Africa, Asia; includes war, forced labor, disease impact debates)

3. Mongol Empire
👉 30–40 million

4. Islam (conflicts under Islamic rule across ~1400 years)
👉 15–40+ million

5. Christianity (conflicts under Christian rule across ~2000 years)
👉 10–60+ million

6. Nazism
👉 ~17 million

7. Taiping Rebellion (religious-messianic movement)
👉 20–30 million

8. Imperial Japan (WWII atrocities)
👉 3–10 million

9. Atlantic & Arab slave trade systems
👉 Millions (hard to total; often 10–20+ million impacted, deaths in the millions)

10. Modern Islamist terrorism (1979–present)
👉 ~200,000–300,000


—

⚖️ Straight takeaway

The largest death tolls come from modern political ideologies and empires, not religion alone

Islam-related conflicts: ~15–40+ million (not hundreds of millions)

Christian-related conflicts: ~10–60+ million