Ridley (Metroid)
One of Adam's final missions to Samus is to finish off Ridley, whom Adam fears might be more dangerous than the Metroids if left unchecked, and claims Samus is the only one capable of stopping him. However, Samus later discovers his corpse after he is killed, having had his energy drained by the Queen Metroid on the Bottle Ship. His mummified corpse turns up again in "Metroid Fusion" on the BSL station, after having apparently been removed from the Bottle Ship by the Galactic Federation and placed in a sub-zero storage room for further research (potentially into further bioweapon applications). It is later infected by an X Parasite, allowing it to gain the ability to transform into Ridley's likeness, known as . Samus later defeats the Ridley mimic and absorbs its Core-X, regaining her signature Screw Attack. What was left of the cloned Ridley's remains were destroyed along with the X when the BSL station crashed into SR388.
Mother Brain
The Boston Phoenix editors Ryan Stewart and Mitch Krpata named Mother Brain the fourth greatest boss in video game history, stating that while she had triumphant roles in "Metroid" and "Captain N", she didn't come into her own until "Super Metroid". They cited the overall quality of the ending for why she was so notable in this role. GameDaily listed Mother Brain as the 12th best evil mastermind in video games. GamesRadar editor David Houghton listed Mother Brain as one gaming's most hideous mums, describing her as looking like a "turd on a stick jammed into the top of a long-dead chicken." In explaining why "Metroid" was among gaming's greatest games, GameSpot editor Avery Score cited the battles with Mother Brain and Kraid, describing the battles as epic. Fellow GameSpot editor Giancarlo Varanini described Mother Brain as "appropriately disgusting". GamePro listed Mother Brain as the sixth most diabolical video game villain, describing the battle with her as one of the most notorious and epic assaults in gaming history. UGO.com listed Mother Brain as one of the runners-up for the "Miss Entertainment", commenting that she has sadly diminished in her attempts to thwart Samus, though they hope that she returns. Mother Brain is also featured in the ongoing GameSpot's All-time greatest game villain. In 2011, "Complex" ranked her as sixth on the list of "most diabolical video game she-villains".