METROID
In the original Metroid, the Galactic Federation hired bounty hunter Samus Aran to infiltrate a Space Pirate base on Planet Zebes, and destroy their leader, the Mother Brain. In order to access Tourian (where the Mother Brain was located), Samus had to defeat the two mini-bosses, Kraid and Ridley. Kraid in the dark, rocky depths of Brinstar. And Ridley, in the lava scorched, ancient Chozo ruins known as Norfair.
Ridley was a difficult opponent to say the least. Players had fight around his hazardous, lava filled lair, all while dodging a barrage of fireballs from the purple beast. However, after a slew of missles and beams, he was finally defeated. Upon the last blow, he exploded into several chunks (Power Ranger style).
At the time, Ridley's past and connection with Samus Aran remained unknown. Of course, players were shocked after they discovered Samus was female, due to the game's ending and the misleading text in the game's manual that stated she was a "he." So, no one knows if this was intentional, or that Ridley's backstory was made up in the later games. At any rate, Ridley was but a lowly boss figure at the time, serving as a less-than-worthy opponent for the bounty huntress. Samus' and Ridley's hatred to one another only grew as the series went on, to the point of arch-rivalry.
Ridley Boss Battle (6:01)