The result of the Spanish treating the natives poorly and forcing them into slavery was primarily that thousands of natives died from slavery and forced labor. The brutal conditions and harsh treatment led to significant population declines among indigenous peoples in the Americas. In addition to the loss of life, there were also long-term impacts on native cultures and societies as a result of colonization.
While Spain indeed became rich by extracting wealth from the American colonies, the immediate consequence for the indigenous populations was devastation from disease, violence, and exploitation.