Final answer:
King Leopold II used exploitation colonialism in the Congo, characterized by land leasing to private entities who perpetrated forced labor and mutilation, primarily for rubber and ivory, which caused a sharp population decline.
Step-by-step explanation:
King Leopold II of Belgium implemented exploitation colonialism in the Congo Free State, using its wealth of resources for personal gain. Despite claiming motives of philanthropy, Leopold brutally exploited the local population. He leased land to private entities, who exercised severe brutality, including forced labor, mutilation, and a reign of terror to meet rubber and ivory quotas. This exploitation led to a significant population decline and international outrage, culminating in the Belgian state taking control in 1908.