Note: There is a similar question about ancient times, prior to 500 AD. So I'll fix the timeline for this question from 500 AD to the time of abolition of slavery in USA.
I've learned (despite best efforts to the contrary by our schools I might add) that slavery was prevalent amongst more than just European colonial nations, and not just in ancient times but all the way up to modern times too, that even white Europeans got taken away in large numbers as slaves prior to the Industrial Revolution, even American Natives practiced slavery. Amongst the Western European civilization (countries in Europe and the United States and Canada), there is well-documented history of rise in public opinion, amongst people belonging to the slave-owner race / religion / culture / tribe, against slavery, of influential religious leaders taking it up as a moral issue, linking it with the dominant religion and advocating against it, of gradual acceptance amongst the culture that slavery is a bad thing, eventually leading to governments / rulers following the people and moving to abolish it.
Are there similar examples of movements in other countries, cultures that practiced slavery natively (ie, they didn't learn it from the Europeans but had it pre-existing), happening between 500 AD to the European-led abolition? I'm not looking for large successful campaigns. Were there significant efforts? Was there leadership?
Note: Taking into context this answer, I'm not looking for matters concerning debt slaves, over-taxation, peasants under feudal lord etc. I mean slavery of the kind where you've kidnapped people of a different place and brought them over against their will, or have assigned that status to a certain group living in your area based on race etc, and they are forced to work for you or to be your sex slaves, there is no avenue for de-slaving, and your culture does not consider them to be equal humans like you.