Watch Superman III (1983) Online

In this third installment, unemployed Gus Gorman (Richard Pryor) discovers a knack for computer programming. After embezzling large amounts of money from the company payroll (through a technique known as salami slicing), Gorman is brought to the attention of his employer, Ross Webster. Webster (Vaughn), a wealthy man who runs a large conglomerate called Webscoe Industries, is obsessed with the computer's potential in aiding him in his schemes for world domination. Joined by his sister Vera and his "psychic nutritionist," Lorelei Ambrosia, Webster blackmails Gorman into helping him.

Meanwhile, Clark Kent has convinced his newspaper to allow him to return to Smallville for his high school reunion. In Smallville, Clark is reunited with childhood friend Lana Lang (Annette O'Toole). Lana is now a divorcee with a young son named Ricky (Paul Kaethler). Although Clark and Lana begin to share affection for each other, Lana's former boyfriend Brad (Gavan O'Herlihy), a former jock and Clark's childhood bully and now an alcoholic security guard, is still vying for her attention.

Back in Metropolis, Webster attempts to monopolize the world's coffee crop. Infuriated by Colombia's refusal to do business with him, he orders Gorman to command an American weather satellite, Vulcan, to create a hurricane to decimate the nation's entire coffee crop. However, Superman flies into the eye of the hurricane, neutralizing it and saving the year's harvest. Perceiving Superman as a threat to his plans, Webster then orders Gorman to use his computer knowledge to create synthetic Kryptonite after remembering Lois Lane's Daily Planet interview from Superman, during which Superman identified it as his only weakness. Gus creates the synthetic Kryptonite, but replaces an unknown element with tar.

Lana convinces Superman to make a personal appearance at her son's birthday party; however, the event becomes a community welcoming for the Man of Steel. Gus and Vera, disguised as an Army general and a WAC officer, give Superman the chunk of kryptonite as a gift, and are dismayed to see that it appears to have no effect on him. However, the compound begins to produce symptoms: Superman becomes selfish, which causes him to delay in rescuing a truck driver from his jackknifed rig and to question his own self-worth. As the Kryptonite takes effect, Superman becomes depressed, angry and casually destructive, committing petty acts of vandalism such as blowing out the Olympic torch and straightening the Leaning Tower of Pisa. Ross, seeing that Superman is presumably out of the way, creates new plans and orders a supercomputer to be built.

Superman sullenly assuages his depression with a drinking binge, but is overcome by guilt and has a nervous breakdown. After nearly crash-landing in a junkyard, he splits into two personas: the evil, selfish Superman and the moral, righteous Clark Kent. The evil Superman and Clark Kent, the embodiment of Superman's remaining good qualities, engage in an epic battle. Although Clark is initially overpowered by his alter ego, he eventually takes the upper hand, feverishly strangling his evil identity until he fades from sight.

After defending himself from an MX missile, he does battle with Gorman's supercomputer, which, after attempting to suffocate him, severely weakens the Man of Steel with a ray of real Kryptonite. Gorman, guilt-ridden and horrified by the prospect of "going down in history as the man who killed Superman", manages to destroy the deadly laser with a fire axe and Superman flees. The computer begins to malfunction, becoming self-aware, defending itself against Gus, and draining power from nearby electrical towers, causing massive blackouts. Ross and Lorelei are able to escape from the control room, but Vera is sucked into the main entrance of the computer and transformed into a cyborg. Empowered by the supercomputer, Vera attacks her brother and Lorelei with beams of energy, which weaken and immobilize them.

Superman returns with a small vial of acid from the chemical plant from earlier in the film. The intense heat emitted by the supercomputer causes the acid to turn volatile, destroying the machine and turning Vera back to normal. Superman flies away with Gus, leaving Webster and his cronies to face the authorities. After dropping Gus off at a West Virginia coal mine, where he gives him a job reference, Superman returns to Metropolis and reunites with Lana Lang, who has decided to relocate to the big city and finds employment as Perry White's new secretary.Flying away into the reaches of outer space, the Man of Steel flashes a smile knowing that all is right with the world he now protects.