Final answer:
Francisco Pizarro decimated the Incan Empire in South America.
Step-by-step explanation:
The explorer who decimated the Incan Empire in South America was Francisco Pizarro. Pizarro, a Spanish conquistador, led several expeditions along the west coast of South America. In 1531, he founded the port city of Lima, Peru, and ultimately captured and executed the Inca emperor Atahualpa in 1533. Pizarro's conquest of the Incan Empire resulted in the decimation of its power and the establishment of Spanish dominance in the region.