From which country did most Colombian slaves come?

It might be surprising, but the answer is Columbia. When the Spanish settled Columbia, they took advantage of the existing population of natives as they did in every other nation of Central and South American they controlled. Local natives, although much more suseptible to European pathogens and suffering from a higher mortality rate died out quickly, but the number of Columbians (in the millions to hundreds of millions) who died in slavery to the Spanish far exceeded logistically the number of Africans who could have been brought over on ships.