Japan wasn't killing their own people.  Nationalist China was but at least partially this was while they were in active civil war against the communists both before and after the war with Japan.

Suharto did kill an incredible number of people but per capita he still falls way behind the Soviets, and China as well as a bunch of other small leftist states, Cambodia probably being the worst example.  We can also talk about Chile and Argentina's RW govts but while the actions may have been wrong the numbers are comparatively tiny.