I wouldn't consider any African nation a success because almost all of them are extremely young. Some of them have very good economics i.e Nigeria or South Africa whilst other nations like Namibia, Botswana, and Senegal have been able to strike a balance. Of course you have The DRC but you also have the ROC where it's almost the complete opposite as far as violence and strife goes. However, I think comparing African nations to western, century old European and Western nations is a stupid metric to go by. Speaking in relative terms, America, when it was as old as most African countries today, was getting its capital burnt to the ground with a brewing civil war not only between abolitionists and anti-abolitionists but between federalists and anti-federalists.