There's no example of a [edit: big-size] "communist" society ("communist" means no central gov't, just self-government by communes). There are examples of "socialist" societies. For example, my family lived in the USSR (Union of Soviet Socialist Republics) - and rose from villagers (who were - before socialism, under capitalism - mostly illiterate i.e. couldn't even read or write) to become far better off under socialism (blue-collar 'non-aristocratic' men & women finally got access to higher education, year-round medicine & hospitals, more meritocratic jobs regardless of race).

As for "mass death" - there was mass death under Capitalism in our region (e.g. French capitalists invaded, looted & massacred people in the 1810s, then British capitalists invaded, looted & massacred our people in the 1850s, then Japanese capitalists invaded, looted & massacred people in the 1900s, then Austrian capitalists invaded, looted & massacred people in the 1910s, then German & Italian capitalists invaded, looted & massacred people in the 1940s, etc). The death toll from Capitalist wars outnumbered anything else. Because Capitalism grows by stealing other continents' & other countries' resources - and to get that, they start wars - and wars bring more "mass death" than anything else.

And that is why the most capitalist countries on the planet (Britain and its offspring, the U.S.) are still the most war-supporting countries on the planet.