When the Qing defeated Dzungar Mongols in 1759, they proclaimed that the Oirats territorial lands were absorbed into "China"  realm in a Manchu language memorial. They expounded the ideology that they were bringing together the "outer" non-Han Chinese like the Khalkha Mongols, Inner Mongols, Oirats  together with the "inner" Han Chinese, into "one family" united under the Qing state. To show that the diverse subjects of the Qing were all part of one family, the Qing used the phrase "Zhongwai yijia"  or "neiwei yijia" , to convey this idea of "unification" of the different peoples. A Manchu language version of a treaty with the Russian Empire concerning criminal jurisdiction over bandits called Qing subjects "people of the Central Kingdom ". In the Manchu official Tulisen's Manchu language account of his meeting with the Torghut leader Ayuka Khan, it was mentioned that while the Torghuts were unlike the Russians,  the  "people of the Central Kingdom"  were like the Torghuts, and the "people of the Central Kingdom" referred to the Manchus. The initial conquest of China by the Manchus was one of the most devastating wars in Chinese history. Examples of the devastation include the Yangzhou massacre; in which some 800,000 people, including women and children, were massacred. Whole provinces, such as Sichuan and Jiangnan, were thoroughly devastated and depopulated  by the Manchu conquest, which killed an estimated 25 million people. Some scholars estimate that the Chinese economy did not the regain the level reached in the late Ming until 1750, a century after the foundation of the Qing dynasty. According to economic historian Robert Allen, family income in the Yangtze delta, China's richest province, was actually below Ming levels in 1820 .
Which saw less casualties, the Yangzhou massacre or the devastation of Sichuan and Jiangnan?
the Yangzhou massacre