He played also Kingpin in the not-exceptionally well-received Daredevil movie, as well as a few other memorable parts including voice acting for animated shows. His mountainous frame was emphasized in films for dramatic effect; he stood 6'5" and weighed over 280 lbs. Truly a screen presence to be reckoned with! (Details on his life and health issues can be found on his Wikipedia page.)
The Green Mile's author, Stephen King, is known to deal heavily with the supernatural themes of Good and Evil, and though often dealing in horror, he also shows romantic sensitivities in showing the power of good to fight evil and win.
His blending of carnal men and transforming spiritual situations is far closer to Biblical themes than one would care to admit at first. And John Coffey's simple and innocent eyes, his understanding of pain and suffering while being black in racist South and falsely accused captivates our moral outrage from the very time we see him, walking meekly and gently with his white guards - guards who are overshadowed not only by his physical size, but by his heart, his compassion and his willingness to die so others can live.
In other words, he played a black Jesus, and we loved him for it.
I will certainly miss this fine actor, as I was a small boy who grew up with big men. Men who may not have been educated, but knew right from wrong, bore injustice with dignity and suffered so others could have a chance at life.
Men who I loved and are now gone.
Rest in peace, Mr. Duncan.
We will never forget you.
This loving tribute was found on YouTube: