Why does Africa not have a great power?

A friend and I got into a little bit of an argument the other day. Talking out loud I mentioned that it was interesting that Africa didn't have a world power. My friend immediately brought up the fact that the Americas had destroyed any chance of Africa developing a power because of the slave trade, ravaging preexisting nations and killing chance for growth.
I am not an expert in history at all, but I was under the impression that for the most part, African slaves were taken from the west coast and center of Africa often by other Africans. This led me to think that why couldn't one of the nations or tribes on the other coast of Africa develop into a world power, or why couldn't one of the slave trading tribes become stronger. I also brought up that I was unaware of really any empires located in Africa besides the Egyptians a crazy long time ago (just a reminder that I am in no way a history expert). I figured I'd post on here in case there is a commonly agreed answer by historians, plus I think the question is interesting. Thanks! TL;DR Why is it that Africa has never developed a great power, and to what extent is that a result of the American slave trade.