Rummel's numbers are considered "considerably inflated".
Rummel himself described his figures as "little more than educated guesses."
-- Wikipedia, citing Rummel, Rudolph (2003) [1997]. "Statistics of Mexican Democide: Estimates, Calculations, and Sources". Statistic of Democide: Genocide and Mass Murder Since 1900 (hardback ed.). Charlottesville, Virginia: Center for National Security Law, School of Law, University of Virginia; Transaction Publishers, Rutgers University. ISBN 9783825840105. Retrieved August 31, 2021 – via Freedom, Democide, War at the University of Hawaii System.
His numbers for China might also be revised downwards.
Keep in mind that this period involves war (WWII and the Chinese Communist Revolution), as well as famine (the Great Famine of 1959--61). The latter has estimates ranging from 15--55 million lives lost. It should be noted that famine was a frequent visitor to China over the previous century, with famines noted in 1810, 1811, 1846, 1849 1950--73, 1876--79, 1896--97, 1907, 1920--21, 1928--30, 1936--57, and 1942--43, prior to succession by the Communists. Most of those involved a million or more dead, several tens of millions. It might be more accurate to describe Communist China as having stopped the history of famine in the country.
It's difficult to differentiate between "government" and "business", particularly where the two entities are strongly interrelated, as with both the Nazi and Soviet states.
You've omitted the case of Britain, who killed off a quarter the population of a country, largely through business interests:
Estimates of deaths in the business-operated slave trade run as high as 60 million, at a time when the total global population was 500m -- 1 billion (1/16th to 1/8 of today's population, very roughly 1/6 to 1/2 that of the WWI--WWII period). Recordkeeping was not especialy precise, as contrasted to the IBM-tallied slaughter of Jews by Nazi Germany.
Governments (via their agents) of the 20th century killed more than 7x more people than were murdered by fellow civilians. This is not counting wars.