"Global", you say? How so?
Sure, the major Western powers like France, Spain, England, The Netherlands, and The United States all employed racially motivated slavery as labor pools for their colonial holdings - and to be fair, their combined colonial efforts reached all across the world. But it was not one single unified system, and while it was far reaching and massive, it was hardly "global" in the proper sense of the word. (Of course this might just be a matter of semantics and differences in our understandings of what "global" means, but the point stands.)
More importantly, you seem to be suggesting that Western European slavery alone somehow uniquely produced class and wealth disparity. Institutionalized slavery existed on every inhabited continent since time immemorial. The Ottomans, the Persians, the Native Americans, the Indians, the Chinese, the major African kingdoms - you name it, they had both slavery and the class and wealth disparity you mention.
And yet, if we stop and examine even more broadly, looking at regions of the world with little or lesser historical slavery, we still see class and wealth disparity. Slavery doesn't cause social injustice - slavery is caused by social injustice. It is a symptom, not the disease. Slavery doesn't occur where people have not already established hierachies and classes - where power and authority is vested in the elite. Rather, it is in fact heirarchy and class taken to the greatest logical extreme.
Slavery is an absurd and abhorrent concept, but that's not to say that non-Western slavery is somehow any different or special in any way. Slavery as a "global" institution is not the work of Europeans alone. Vast proportions of that global institution were established and entrenched by others. Look almost anywhere that existed in a feudal state at one period or another (this ends up being pretty much the entire world) and you will find institutionalized slavery in some form or another. Anywhere a king-like figure ruled, anywhere the wealthy elite held power, anywhere the aristocracy demanded final authority, you will find slavery.
The only thing that might make Western slavery at all unique or different than all the other kinds of slavery are its specific racial and religious motivations, a la "The White Man's Burden". Except it doesn't - enslaving others based purely on their race or religion actually dates back to Biblical times and before.
In fact, the one place where Western slavery is at all unique is in their being the first to strive to abolish it. The Rennaisance and the Enlightenment were chiefly concerned with Humanist values, with highly Liberal viewpoints on the nature of humanity, and it was these new ideas flowing throughout Europe that directly fueled the Abolition movement. In many other parts of the world, slavery would continue unabated for quite some time, often remaining legal for more than a century longer than in the West.