The archilles heel of both regimes is corruption. But its easier to describe than to cure the disease. This is the number one restraint on the continued growth of the Russian and Chinese economies. Kleptocracies sooner or later collapse of their own inherent rottenness. Both Putin and Xiping will be unable to completely extirpate it.
Mao said that all political power came from the barrel of a gun, and this is how these regimes ultimately operate. What will occur in the end is not a collapse of their regimes, but a world war. Chinese generals have already said that, in the event of an economic collapse, they would focus the frustrations of their people “into a fist, striking outward.”