Two actors come to mind when I think of who depicted their roles as the author intended, Leslie Howard and Marlon Brando. Leslie Howard portrayed Henry Higgins in Anthony Asquith and Leslie Howard's 1938 cinematic version of George Bernard Shaw's 1913 Pygmalion, and Marlon Brando portrayed Stanley Kowalski in the 1951 Elia Kazan film version of Tennessee Williams' 1947 A Streetcar Named Desire. Both men depicted their roles with great intensity and are two of the finest actors in film.
First let us look at Leslie Howard's depiction of Higgins in his 1938 film Pygmalion. Leslie Howard to me is Henry Higgins. There has been no one else to copy the role. Rex Harrison played the part in 1964 in George Cukor's 1964 My Fair Lady. Harrison did a good job, but his portrayal of Higgins was unrealistic.
Leslie Howard's version of Higgins was real. He depicted Higgins as a real person--a phonetics professor who could speak perfect English, but who was far from perfect. Bernard Shaw never intend for Henry Higgins to be perfect or larger than life when he created him in 1913. Higgins was to be a phonetics professor who could pinpoint the location of someone's home in England by his or her voice. Outside of his field he was not to be as perfect. Leslie Howard bought this out in his depiction of Higgins.
Leslie Howard had a way of showing Higgins' flaws. Higgins did not know how to properly act around women; he had no manners. Howard had a way of making expressions and giving Higgins a human quality. Rex Harrison gave Higgins an inhuman quality. He made Higgins a perfect professor and a person who always know what was going on-not the same character Shaw created in 1913.
As for Marlon Brando in A Streetcar Named Desire, released in 1951, he too depicted his character as conceived by the author. Tennessee Williams created a complex and brutish character in 1947, when he dreamed up Stanley Kowalski. Stanley was a poor hard-working man in New Orleans who liked to come home and enjoy beer and relax. He liked to drink and play poker with his friends. Stanley was also an abusive person who, while drinking, could become very violent. Even though Stanley has his bad qualities, Tennessee Williams wanted his audience to feel sympathies with Stanley
Brando depicts Stanley in that very way. He shows Stanley's brutish and violent side, yet one cannot help but feel sorry for him. Brando has a way of using his face and body language to show his feelings. Even when Stanley is throwing Blanche's things around and acting like a jerk, Brando makes this seem humorous and makes the viewer laugh at his bad behavior.
Only Marlon Brando could have played this part the way that Tennessee Williams meant it to be played. No other actor is ever thought of when the name "Stanley Kowalski" is mentioned. No one else has ever given the character of Stanley the true identity he was meant to have.
Leslie Howard and Marlon Brando would get my vote for best depictions of an author's conception. They both brought their characters to life in a way no one else could. Both authors, I am sure, would agree.