Mao's an interesting one, he's still viewed largely favourably in China - still on their money, and most Chinese will say that he did more right than wrong.
On the other hand a LOT of people were killed. A very lot.
The numbers usually include the millions who died in the great famine (like 30-50 million I think), which while undoubtedly a direct result of the changes that were made as part of the "great leap forward" and being taken in by the charlatan Lysenko, it is difficult to know whether Mao was actually aware of the famine or the extent of it, as all the regions still were reporting grain surpluses for fear of being reprimanded.
So definitely their fault, but how can you compare that to sending 6 million people to be executed in gas chambers?
China's whole history is ridiculously brutal. The death toll in their conflicts, genocides and uprisings make most European conflicts look like a walk in the palk (untl the 20th C)