A cadre of 100 Spanish troops in armor with guns and swords could easily defeat 500 natives with stone-tip spears.
Once you reach that level of military advantage, all you need fear is a cadre of troops willing to engage in the cold calculus that enough of them could eventually wear you down and kill you all.
The natives didn't have any troops capable of withstanding that sort of carnage and a style of warfare they were absolutely unused to.
Look at Pizarro and Peru. 200 Spanish troops defeated an army of tens of thousands.
21 men with rocks beats one man with an M4 and 20 rounds every time, IF 20 of them are willing to die.
In cases of 100 to 1 odds, small military advantage is more powerful as a pschological weapon than as a real advantage, but a real advantage never the less.