There were MILLIONS of victims in that traffic.
But if you really want to slap around Europeans take note of the several tens of thousands of Sa'ami from the Sapma who were kidnapped by the Swedish Empire and sent to America to cut trees.
Then, if you can work that one around in your head, consider Thailand ~ they were busy from the 1300s working away in Indonesia making slaves of everybody they could catch. Those people were put to work harvesting spices.
Did I miss somebody in that 500 year period? Oh, yeah, the Iroquois spent a lot of time in the Ohio Valley attempting to reduce all the indigenous peoples there to being nothing but tributaries to the Iroquois nations! That didn't end until the mid 1600s when a very nasty plague hit them.
Regarding the African kings who sold their citizens ~ they sold an awful of them!
This is like Holder's daffynition of racial discrimination: "It only qualifies as racial discrimination if it is white discriminating against black."
In this case it counts as slavery only if the bad guy is white skinned.