Complex sentence: Leopold II (9 April 183517 December 1909) reigned as the second King of the Belgians from 1865 to 1909 and became known for the founding and exploitation of the Congo Free State as a private venture.
Split into simpler sentences: Leopold II (9 April 183517 December 1909) reigned as the second King of the Belgians from 1865 to 1909. He became known for the founding and exploitation of the Congo Free State as a private venture.