The defeat of the Paris Commune might be one to look into. Marx writes all about it in The Civil War in France. Not 100% sure on this but IIRC the Thiers government murdered more people in their counterrevolution in a matter of days/weeks than were killed in the entirety of the Reign of Terror. That last point is salient because all through the 19th century, the Reign of Terror served nearly the exact same purpose that the "communism killed 100 million people" line serves today. It was a cautionary tale reactionaries would point to as evidence as to why you can let people try and have a better future for themselves.