The movie, the Hustler uses pool as a background to the on screen dramatization of human faults and the ability of some to overcome their faults to some degree and find redemption somewhere in their soul, where, for others, redemption is a fleeting occurrence, and they remain deeply flawed in their make- up.
Fast Eddie develops from a cold hearted hustler to someone who understands remorse and actually feels it and can express it regarding the fate of Sara in the closing scene with Bert. Bert remains a money driven shark who finds within himself a small shred of human feeling when he allows Eddie to leave the final pool hall scene with his winnings and without a terrible beating. Sara rises above her alcoholic state to provide comfort to a wounded Eddie after his first brutal loss to Fats, and his subsequent bar room broken thumb encounter. Yet Sara cannot help herself as she falls back into the depths of her damaged sense of self worth due to her birth defect and subsequent alcoholism; thus, her encounter with Bert in the hotel room leaves her as a tragic figure who can only find death as a solution to a terribly painful life.
If you have spent enough time in pool halls, you have met all of these characters along the way.
Two other movies that used similar characters, but different backgrounds ( one was the waterfront and mob driven labor control, the other was the boxing ring) - On the Waterfront and Raging Bull - also were based upon deeply flawed human characters that either found some degree of redemption in life or lost their souls to their lifetime personal battles. I don't feel that the reviewers here quite understand that black and white filming, the use of shadowing and the actual lack of light in many scenes, the music scores, etc. - while spanning over 30 years between these three movies- are all central to how the director was creating mood so vital to each film's success.
The COM movie was never directed by Scorsese to take on these other three giant films, Vincent Lauria was NOT Terry Malloy (Marlon Brando), Fast Eddie ( a young Paul Newman) or Jake LaMotta ( Robert DeNiro)