

An experiment on a simpleton turns him into a genius. When he discovers what has been done to him he struggles with whether or not what was done to him was right.
Acting
Cliff Robertson's Oscar-winning transformation from childlike to brilliant to broken
Direction
Ralph Nelson's unflinching commitment to the source material's bleak honesty
Writing
Daniel Keyes' novel adapted with devastating fidelity

Director
Ralph Nelson
Trivia, insights & behind the scenes
Cliff Robertson bought the film rights himself after seeing a TV adaptation, then spent eight years getting it made. He won Best Actor for a role nobody else wanted to touch.
This predates every 'enhanced human' trope from Limitless to Lucy, but treats the subject with crushing humanity rather than superhero spectacle.