it depends on what you categorize “success” as. There have been various Socialist states that have achieved successes, but no state on the face of the planet is free from failure - the failures of these states are what anti-communists will posit when arguing that socialism has “failed”, even if the failure of the state doesn’t constitute a failure of the socialist system. China and the Soviet Union achieved high employment rates, low homelessness rates, the same or higher caloric intake as the United States, technological leaps the west couldn’t achieve, and social strides that again the west couldn’t achieve. They achieved variations of Socialism, their own ways. But, anti-communists will tell you both abandoned socialism, and both failed at being socialist states.

Cuba is, perhaps, one of the better examples of home-built Socialism. Despite the sanctions, they’re a leader in human rights, a leader in medical studies and a major exporter of medicine and doctors to the third world, boast low unemployment and homelessness, and have wonderful social rights. This would be a successful implementation of Socialism - and arguably just as successful as the Soviet Union or China.