I think the worst impact European colonization had on Africa was that they didn't dived based on ethnic groups and religion they based it on what the land had to offer them. The people are used to being around others that believe in the same thing as them then all of a sudden Europe came and blended ethnic groups in a way they never have. The natives had been there for thousands of years and didn't like the way there were divided.  They had different beliefs and traditions and mixing them caused conflict and many deaths. It also led to racism which in turn caused many conflicts against the Europeans and even more deaths.