Which country dominated early slaves trade in South American factor contributed to most slaves trade?

Spain

Explanation:

West Africa has been a major slave trade place for three centuries. During the 17-18 centuries, when the slave trade reached large scale, approximately 15 million slaves were taken out of Africa, of which at least five million died on the way. Of the vast number of enslaved Africans who reached the Western Hemisphere, 388,747 slaves arrived in North America; 1.3 million slaves were delivered from Africa to Spanish Central America. Then about 4 million fell into the British, French, Dutch, and Danish colonies in the Caribbean and 4.8 million were brought to Brazil.