the Russian and Cuban systems primarily changed due to modernization and not anything the system did (don’t make the liberal mistake of assuming the advances of modernity are inherent to the system at the time), but China actually got Worse until it “liberalized” its markets and started pulling foreign capital investment

Yes, but transforming power structures doesn’t equate to killing opponents. It is neither sufficient nor necessary. The success of some revolutions shouldn’t be attributed to lethal violence.