A nemesis is a seemingly unbeatable or unconquerable enemy, often used as a foil to the protagonist, where interaction between the hero and his antagonist forms the main conflict of the story.
A name used for some installments of the Gradius video game series, mainly in Europe.
Resident Evil 3: Nemesis (original Japanese title: BioHazard 3: Last Escape). Nemesis is the namne of a deadly biomechanical assassin made by the Umbrella Coorporation. Resident Evil: Nemesis was also a working title for the movie Resident Evil: Apocalypse.