Do you have a source for the 100 million number? The highest scholarly estimate I know for the death toll of the Great Leap Forward is
45 million. Even when the Cultural Revolution, land reform and all the other campaigns of political repression are included, the total number of deaths is probably not much more than 50 million. Also, 100 million would have been something like 1/6 of China's population in the 1960s. I don't see how the PRC could kill that many people and not collapse.
It is also unlikely that the KMT would be much better than the Communists. Chiang Kai Shek
killed at least 500,00 people by deliberately flooding the Yellow River, an event which significantly contributed to the
1942-3 famine in Henan. The KMT also killed thousands in several
anti-Communist purges and in the
Taiwanese White Terror. If the KMT had won the civil war, the resultant white terror would probably have killed at least hundreds of thousands. Absent any sort of land reform, KMT-ruled China would experience immense poverty and inequality. In OTL India,
tens of million people starved between 1947 and 1979, I wouldn't be surprised if a similar number of Chinese would have perished. China also saw significant increases in life expectancy and decreased death rates relative to India. That might not happen if the KMT had won.
This post should not be read as an endorsement of the Communists. The PRC's government has committed, and continues to commit, great crimes against the Chinese people. But that does not mean that the KMT would have been good