The Inka (sometimes called Inca), definitely. They set up a collectivized society so efficient that they had huge surpluses of manufactured goods and so much spare labor that they built highways all over the Andes. Their military was without peers in the area and conquered all major nearby civilizations.

Of course, there's the obvious point of their empire falling to Pizarro, who had only a few hundred men. There were numerous causes of that, not least of which were the massive numbers of deaths from plague, the technological advantages of the Spaniards, and the power struggle under way for control (during which one side [temporarily] allied with the invaders).

Still, at their height, the Inca army could compete with most others in the world at the time, even considering their lack of worked metal, mounted troops, and siege engines.