Shaka Zulu. A brilliant strategist, he realized the shortcomings of Native warfare (mainly ineffective dispersed archery and throwing spears) and copied the Greek Phalanx and the Roman Legions. He had his soldiers discard the clumsy sandals that slowed running and made his warriors toughen their feet which lead to much more mobility. He adopted short stabbing spears (much like the Roman short sword) and shields and the enveloping movement of the greek phalanx. While initially outnumbered he destroyed all in his way (he was smart enough not to engage the white settlers-something his successors learned painfully at Blood River as the Boers engineered a brutal payback for the treacherous murder of their leader and his family Piet Retief.
Pretorious's Boers suffered several wounded-the much larger Zulu forces lost thousands so Pretorios is also in the running for a top slot in history's ranking of Generals
But Shaka managed much more. He displaced 25% of all sub saharan native populations with his conquest. Given what he had to work with, his brilliance is in rare company