Who is Mr. Big from Live and Let Die and what is their importance?

Mr. Big is a Haitian-born gangster now living in Harlem in New York City, Mr. Big is a large African American, forty-five-year-old man, half Haitian and half French. He runs a crime outfit in New York. His real name is Buonaparte Ingace Gallia (initials B.I.G.). He is a follower of Voodoo and is believed by many to be the Zombie of Baron Samedi, the Prince of Darkness. During World War II he worked for the Office of Secret Services. He is a known SMERSH agent, working with the Soviets.