Generally these countries already had massive wealth disparity so keep that in mind, with a few landlords and the rich ruling over vast amounts of a mostly rural populace.
North Korea was a lot more equal than South Korea when it was formed although I’m sure it’s changed since then, but they don’t let people in so there’s not many official figures. China is basically a capitalist country now, although notably it’s income inequality rose more when it implemented these market reforms that made it more capitalist. It’s wealth inequality is less than the US’s, or about the same, anyway.
Cuba was a lot more equal after the revolution than before. They basically removed homelessness, fed everyone, gave everyone health care, etc. It’s commonly known that the Batista era was filled with graft, rich landowners and club owners, and corrupt government officials while most of the countryanguished in poverty. Inequality has only risen when they had to implement more capitalist-like market reforms after the Soviet Union fell and they lost their major trading partner.
Vietnam had also done well at that front, increasing growth with only slight increases in inequality, doing better than China on that front. They’re still worried about it after implementing market reforms as well but are working on it, and have still done better than other countries.
Notably Social Democratic countries like the Nordic ones have also done well in terms of wealth inequality, but like these other ones examples, it can trend worse when increasing - privatization or similar capitalistic reforms. Some of these countries like Norway also have even more publically owned goods and companies than countries people think of as socialist, like Venezuela.
Speaking of, Venezuela had the lowest inequality in South America for a long time, although crashing oil prices has impacted that.