Duncan grew higher inside one-parent menage around Chicago. He universally wanted to work, however experienced to drop away from a Communications program at Alcorn State University to support his personal while his mother became complaint. Duncan's big frame of Sextuplet foot Five around (Single.96 m) & weight of 300 pounds (136 kilogram) helped him inside his jobs digging ditches for the Humans's Gas service & existence the bouncer at different Chicago clubs. Across working at the clubs, he was suspire for a security job & ended higher inside Los Angeles.

He took more security jobs patch around Los Angeles when trying to develop occasionally acting act inside commercial message. At length he was cast inside a hike-nonspeaking role inside Ice Cube's Friday. In the period of this instance, he continued to operate as a bodyguard for celebrities rather Will Smith, Martin Lawrence, Jamie Foxx and LL Cool J, all the while doing minor role around television & films.

Within 1998, Duncan was cast as Bear in the picture Armageddon, where he struck higher the friendly relationship by owning castmate, Bruce Willis. It was Bruce Willis' influence that helped him for his break role in the Frank Darabont-directed, The Green Mile, a role which netted him an Academy Award nomination and the Golden Globe nomination.

Duncan so was cast within the string of films that helped to establish him as a star: The Whole Nine Yards, Planet of the Apes, The Scorpion King (where he starred alongside his friend, The Rock) and Daredevil as The Kingpin. Duncan has too provided his voice for the total of roles including Brother Bear and the streaming games Demon Stone, SOCOM II: U.S. Navy SEALS and Soldier of Fortune.