Ethiopia
With over 2,300 tanks, and 800 armored personnel carries, Ethiopa has one of the strongest armies in Africa. With around 185,000 soldiers, Ethiopia is not lacking in manpower either. One caveat is that much of the equipment is from the Soviet times, and a good chunk of it might not work.
Ethipian soldiers, have a reasonable amount of combat experience, from constant skirmished with neighboring Eritrea.