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 (fictional species)
"Game Informer" called the Metroid their favorite alien race in video gaming, praising how their appearance is "truly alien" and that they "pose an immediate and real danger" when they appear. "Hardcore Gaming 101" called their design "iconic", and praised their first appearance in the original "Metroid", saying that it was "a moment of shock and terror almost unlike anything in any other NES game", especially if the player did not know how to beat them.