Meanwhile, the problem with communism is that it relies on everyone having aligned incentives on a nation-state level, which is a pleasant fiction and can only be achieved through authoritarian coercion.
Capitalists would argue that between capitalism and socialism, capitalism is the one that better accounts for greed, as it generally has laws to con strain it but otherwise uses it to generate all the production that's the hallmark of modern society, division of labor, economy of scale, technological advancement, etc. Socialism doesn't really deal with greed, it just sort of wishes it away. That's why so many societies that have started down the socialist path have become at best poor and at worst authoritarian murder factories like the Soviet Union, Maoist China, Chavist Venezuela, the Khmer Rouge's Cambodia, etc.