In almost all cases other than Africa they almost wiped out the inhabitants of a certain part of the country, and pretty much ethnically cleared an area for European settlers. Only leaving behind a minority that would either assimilate or not be a threat.
But they didn't do this with Africa, why?
The British didn't kill everyone they met. It was disease that killed almost all natives that Europeans met. The Africans were ether too dispersed or already had some immunity to the diseases that the Europeans brought.
Edit I'm not denying that there was genocide. I'm just stating the vast majority of deaths are attributed to diseases that came with the Europeans.