Ridley (Metroid)
Often considered one of the most memorable Nintendo villains, Ridley has been a mainstay of the series, having appeared (through various incarnations) in almost every "Metroid" game to date (all but "", "Metroid Prime Hunters" and ""). He has also appeared in the "Super Smash Bros." series, however, he had not been made a playable character until "Super Smash Bros. Ultimate" in 2018, making it also the first game overall to have Ridley as a playable character.
Metroid Prime 3: Corruption
The events in "Metroid Prime 3: Corruption" take place six months after "". The game's protagonist, Samus Aran, is a bounty hunter hired to assist the Galactic Federation during its ongoing conflict with the Space Pirates. After facing initial defeat on the planet Zebes during the events of the first "Metroid", the Space Pirates sought to gain power by using a newly discovered mutagen called Phazon. However, Samus managed to disrupt their operations throughout the "Prime" trilogy and ultimately allowed the Galactic Federation to confiscate and replicate their Phazon armaments.