I don’t know of any actual genocide that Genghis Khan committed, though there are a few cities that were completely obliterated. It didn’t take long before most cities started to surrender before the red tent went up, and all did before the black tent went up.
Genghis Khan actual did bring what these people call law and order to regions infested with war, chaos, and banditry. One contemporary had even said a merchant could walk from one end of the empire to the other with a vase full of valuables on his head with no fear of being robbed.
Genghis Khan may have been brutal, but he was brutal against other actually brutal rulers, particularly against the Chinese kingdoms, because he, his mother, and his brothers were left to fend for themselves in the wilderness after his clan became too powerful in the eyes of the Chinese, and support was withdrawn from his father who was chief at the time. His uncle (if I’m recalling correctly) took over as chief of the clan and banished them. When Genghis Khan learned of how the Chinese were doing this for the last several centuries with the clans north and west of Chinese lands, funding the weak clans against the strong, and abandoning them to fund new weak clans, he decided not only to form his own new clan for the survival of his family and others who were banished, but to destroy the Chinese kingdoms’ ability to do this again in the future.
All of which drew more attention and require more conquest just to survive.
No, not nearly the nicest of men. But how much brutal and vicious bloodshed would have occurred if instead of the wealthy and powerful assuring their personal position, cultures actually worked to bring everyone into prosperity? Believe it or not, Genghis Khan tried that. To help everyone who worked to create something be able to keep working, instead of the vast majority working to support a small contingent above them, while also fighting for that same small contingent’s position right there on their shoulders.