It’s not unique. It’s called genocide in conjunction with religious imperialism.
If you kidnapped me and locked me in your basement for 50 years then decided to go down to the police station and confess. Then free me from my prison, in your basement which you created. I would not say you abolished kidnapping.
Whether slavery existed all over the globe is irrelevant to European participation in it. It’s just wrong. It is so sad. I grieve for the European in the world after this one. May Mercy and Grace be upon you all.