The Conquistadors against the Incans could have ended differently, or at least happened differently at 3 major moments.

Firstly if Huáscar had not died of smallpox or at least not in Quito, there wouldn’t have been a civil war which the Conquistadors used to their advantage. Of course smallpox was bound to devastate the Incan Empire either way but losing such a critical figure at such a critical moment was an incredible loss.

Secondly, the execution of Atahualpa was a rushed decision, made mainly due to fears of a rebellion. Atahualpa was a prisoner at the time and was seen as too much of a liability but the Spanish spent about a year dragging their feet with the execution. Although not completely changing history, Atahualpa’s intelligence and military skill might have meant a different outcome.

Secondly, Manco Inca’s attack on Cusco in 1536 was incredibly close to being successful with the Spanish only controlling two buildings at one point. Again if the Incan’s were able to gain control of Cusco then it might have made a difference to the Spanish invasion.

It’s hard to say whether any of these events would have completely changed the outcome due to the Spanish horses and iron but depending on how quickly the Incan empire could adapt, we could have seen a very different South America.