Greatest African Empire/Kingdom?

I have to go Mali because of the power and wealth. Honorable mention to the Zulu Empire for their fight against the British and Ethiopia for resisting colonization.

Missing the best empire of all time "Central African Empire" Hail Bokassa I

Egypt hands down. No option for Egypt? Okay then, Ehtiopia. . . You played my hand

I think the greatest kingdom without a doubt would be Egypt or Ethiopia. However, I lean more towards Ethiopia because Egypt was dominant from the 3rd century B.C to it's invasion by the Assyrian empire and was constantly occupied by foreign governments, although Egypt was certainly still powerful under the Mamluks and Ottomans. Ethiopia, by contrast, had a kingdom of Ethiopia descent since the beginning and held off many invasion up to the 19th century against the Italians, one of the only native African empires to successfully do.

What's the difference between Ethiopia and Aksum? (Maybe I should just Wikipedia it, but seems more fun to ask you guys.)

The Aksum Empire was based around a different ethnic group in a different city, now known a Axum. Axum is in the Tigray ethno-region of Ethiopia.