The importation of slaves had different impacts on different groups.  For example:

• The slaves themselves were subjected to brutal conditions both while being imported and once in the Americas.  Some places were worse than others, but all slaves ended up in a system that was fundamentally brutalizing.
• African societies were devastated.  They lost many people, most of whom were in the prime of life.
• The whites in the places that received the slaves were hurt in at least a moral way.  Slavery allowed them to treat other people like tools.  This is not good for a person's sense of compassion or for their morality.
• The American societies were forced to deal with (later in history) the consequences of slavery.  Many of them have to deal with multi-racial societies in which there are still tensions between blacks and others.