The Lawnmower Man (1992)

The eccentric Dr. Lawrence Angelo puts mentally disabled landscaper Jobe Smith on a regimen of experimental pills and computer-simulated training sequences in hopes of augmenting the man's intelligence. In time, Jobe becomes noticeably brighter and also begins to fare much better with the opposite sex. As he develops psychic powers, he realizes that those around him have taken advantage of his simplicity his whole life, and he plots a bloody revenge.