Not just Europeans, jc.

"In the Middle East, and particularly in Iran, Genghis Khan is almost universally condemned as a destructive and genocidal warlord who caused enormous destruction to the population of these areas.[68] Steven R. Ward wrote that "Overall, the Mongol violence and depredations killed up to three-fourths of the population of the Iranian Plateau, possibly 10 to 15 million people. Some historians have estimated that Iran's population did not again reach its pre-Mongol levels until the mid-20th century."[69]

In Afghanistan (along with other non-Turkic Muslim countries), he is generally viewed unfavorably, though some groups display ambivalence as it is believed that the Hazara of Afghanistan are descendants of a large Mongol garrison stationed there.[70][71]

The invasions of Merv, Samarkand, Urgench, Nishapur, Bamyan, Balkh and Herat among others caused mass murders, such as when large portions of Khorasan Province were completely destroyed. His descendant Hulagu Khan destroyed much of Iran's north and sacked Baghdad, although his forces were halted by the Mamluks of Egypt. Hulagu's descendant Ghazan Khan once returned to beat the Mamluks and briefly gain the control of Syria, but were eventually defeated. According to the works of the Persian historian Rashid-al-Din Hamadani, the Mongols killed more than 70,000 people in Merv and more than 190,000 in Nishapur. In 1237, Batu Khan, a grandson of Genghis Khan, launched an invasion into Kievan Rus'. Over the course of three years, the Mongols annihilated all of the major cities of Eastern Europe with the exception of Novgorod and Pskov.[72]

Giovanni de Plano Carpini, the Pope's envoy to the Mongol Great Khan, travelled through Kiev in February 1246 and wrote:

“ They [the Mongols] attacked Russia, where they made great havoc, destroying cities and fortresses and slaughtering men; and they laid siege to Kiev, the capital of Russia; after they had besieged the city for a long time, they took it and put the inhabitants to death. When we were journeying through that land we came across countless skulls and bones of dead men lying about on the ground. Kiev had been a very large and thickly populated town, but now it has been reduced almost to nothing, for there are at the present time scarce two hundred houses there and the inhabitants are kept in complete slavery.[73]
"



and that was a larger percentage of the world population, by far.