The weapon commonly used to defeat the final boss in the original Resident Evil is the Rocket Launcher. During the climactic confrontation with the Tyrant, a rocket launcher is delivered to the surviving player character for the finishing attack.
The weapon is associated with the game’s dramatic ending sequence rather than ordinary exploration. Ammunition is scarce throughout the mansion, so players usually conserve powerful weapons and supplies for major enemies. The Tyrant encounter reinforces that resource-management design by making the final battle feel different from earlier fights.
The original Resident Evil’s ending helped establish conventions that appeared in later entries, including a timed escape and a powerful weapon supplied near the finale. The rocket launcher should not be confused with the grenade launcher, which is another high-powered weapon available during the game and uses several kinds of ammunition.