Final answer:
Bartolomé de Las Casas was a former encomendero turned reformer who spoke out against the encomienda system and advocated for the humane treatment of Native Americans, ultimately influencing the New Laws of 1542 aimed at ending the system.
Step-by-step explanation:
Bartolomé de Las Casas, initially a participant in the encomienda system, underwent a profound transformation and became a vocal advocate for the rights and humane treatment of Native Americans.
As a Dominican friar, de Las Casas was deeply affected by the violence and brutality he witnessed against the indigenous peoples by the encomenderos. His advocacy was encapsulated in his book, A Short Account of the Destruction of the Indies, where he vividly described the atrocities committed by the Spaniards.
Las Casas's efforts culminated in the implementation of the New Laws of 1542, intended to reform and eventually abolish the encomienda system, though these reforms were met with significant opposition and violence in the colonies.