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.
T.H.U.N.D.E.R. Agents
With the threat of the Subterraneans ended, new villains appeared in the original series. Issue #9 introduced S.P.I.D.E.R. (Secret People's International Directorate for Extralegal Revenue), the main villains for the rest of the series. Other menaces included the Iron Maiden, an armored mastermind (introduced in the first issue as a possible love interest for Dynamo) who worked for the Subterraneans; Andor, a fast-healing telekinetic superhuman created by the Subterraneans who was introduced in "Dynamo" #1; along with Red Star (Communist menace) and others.