Amazing Fantasy #15 by Stan Lee

A shy, academically gifted teenager is bitten by a radioactive spider and develops superhuman strength, agility, and a precognitive “spider-sense.” After initially exploiting his new powers for personal gain, a tragic failure to stop a robber leads to the murder of his beloved uncle and forces him to accept responsibility for using his abilities to fight crime, adopting a masked identity and confronting the moral and practical challenges of being a hero.