A fairly good overview for a shot article.
The Aztecs and other American Indians kept slaves as well.
The Aztecs ate those who were surplus or problems, from the contemporary account (the only one we have) by Bernal Diaz in The Discovery and Conquest of Mexico.
The Arab world took ten times as many slaves as Europeans did over a much larger time frame period. And they treated them so badly that there is almost no genetic legacy of that group as compared to the “black” populations in North and South America or the evident mixing throughout the Americas.