Not trying to start an argument: what are examples the biggest successes of communist regimes/movements?

In China a notable example is the raising of the median income significantly, to almost 40k USD last I checked, essentially lifting a huge amount of people out of poverty.

The USSR raised life expectancy and HDI significantly, and when it collapsed both fell sharply in the resulting countries.

Was that income after Deng opened up China as the world’s manufactory? That giant amount of support from capital seems to be more effective than any decision communism made.
Reform and Opening Up was a plan devised by communists to more quickly achieve communism, and was made in such a fashion that built upon the existing socialist system, not undermining it.