While the serfs and peasants of the land were very poor, as well as tied to the land they worked on, there appeared to be no large slave trade in Medieval Western Europe, while these regions often had slaves in Roman times. While slavery did gain traction with the age of Exploration, what brought the end of slavery to Medieval kingdoms such as France, England, Castile, or the Holy Roman Empire?
I'd point you to several excellent answers 1 2 3 by /u/textandtrowel about slavery in the middle ages, and the slave trade in venice.
also, /u/sunagainstgold talks some more about the venetian slave trade in this comment
Of course, these answers touch on Francia peripherally, so I hope Textandtrowel or Sunagainstgold will see this thread and provide you with information specifically about England or the Holy Roman Empire.