The correct answer to this open question is the following.
The consequence of Columbus's voyages that had the largest impact on American Indians was the many diseases that the Spaniards conquerors brought to the Americas. These diseases killed thousands of Native Americans. Historians believed that 1/3 of the total Native American population disappeared due to the many new diseases brought by the European conquerors. We are talking about diseases such as chickenpox, smallpox, malaria, and influenza. The Native American Indians were clean and healthy people. The Europeans were totally different.