Is Fascism a religion, is Communism a religion .
Religion and politics often intersect, e.g. religious beliefs can determine and support one's politics. Also one's political ideology can determine one's support of a religion or decrying of another.
But they can also conflict, so that the reverse is true., e.g. politics can deny the practise of religion, and vice-versa.
This article surveys some of the philosophical problems raised by the various ways in which religion and politics may intersect.
https://iep.utm.edu/rel-poli/
These 2 ideologies were the biggest killers of the 20th century and not a Christian among them.
Apparently famine, colonisation and democide (government killing its own people) were the biggest killers. Sometimes famine is 'man-made' in that politics can exacerbate the effects of famine.
WAR ISN'T
THIS CENTURY'S
BIGGEST KILLER
By R.J. Rummel
Our century is noted for its absolute and bloody wars. World War I saw nine-million people killed in battle, an incredible record that was far surpassed within a few decades by the 15 million battle deaths of World War II. Even the number killed in twentieth century revolutions and civil wars have set historical records. In total, this century's battle killed in all its international and domestic wars, revolutions, and violent conflicts is so far about 35,654,000.
Yet, even more unbelievable than these vast numbers killed in war during the lifetime of some still living, and largely unknown, is this shocking fact. This century's total killed by absolutist governments already far exceeds that for all wars, domestic and international. Indeed, this number already approximates the number that might be killed in a nuclear war.
https://www.hawaii.edu/powerkills/WSJ.ART.HTM
The overarching source of loads of similar material
https://www.hawaii.edu/powerkills/20TH.HTM
One overall conclusion that can be drawn is that mankind is becoming more violent, not less so.