Estimates suggest that the Gini coefficient of the whole world is around 0.7. To put that in perspective, a relatively equal country like Sweden has a Gini coefficient a bit below 0.3; the coefficient for the US was around 0.35 in 1950 and is a little over 0.4 today; Brazil is at 0.6.
South Africa is around 0.7, which makes it one of the most unequal countries in the world, and certainly the most unequal large country. See Global inequality by Branko Milanovic (2016), especially Chapter 3, titled ‘Inequality among countries: from Karl Marx to Frantz Fanon, and then back to Marx?’.