I am looking for a word or phrase to communicate someone who has committed what amounts to crimes against humanity, but who is not a politician or a soldier or military leader.
I want to describe the rubber barons (not robber barons) who exploited people in the Amazon basin at the turn of the 20th century. Not only did they enslave indigenous people to collect latex, but they also kept sex slaves, trafficked in human beings, drove out populations, murdered people, razed villages, etc. Here is a brief reference.
Someone who does this things might be called a war criminal, but these rubber barons were not military leaders, nor was there a war.
The term "slave driver" comes to mind, but slave-holding is not the limit of what they did, and also it has the connotation of a boss or overseer who simply works their employees too hard.
One might call them a "monster" or similar name, but that doesn't indicate the scale or specificity of their evil deeds.
Is there an apt phrase that would indicate the situation?