Ridley

Ridley is the leader of the Space Pirates, and one of the main villains in the Metroid series of video games. He is directly responsible for the murder of Samus Aran's mother and partially responsible for the death of her father. In several instances, Ridley appears as an upgraded cybernetic version of himself called Meta Ridley. In addition to the Metroid series, Ridley has made an appearance in all games in the Super Smash Bros. series (aside from Super Smash Bros. for Nintendo 3DS), as well as in Nintendo Land in animatronic form.

Super Smash Bros.
In Super Smash Bros., Ridley can occasionally be seen flying in the background of the Planet Zebes arena.

Super Smash Bros. Melee
Ridley also makes a brief appearance in the opening cinematic of Super Smash Bros. Melee, where he can be seen battling his archenemy, Samus Aran. A trophy of Ridley can also be obtained in this game.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Ridley is fought twice in the Subspace Emissary. The first time he is encountered, he is fought by Samus and Pikachu. As the two reach the exit to The Research Facility, where her Power Suit had been held, Ridley appears without warning and snatches up Samus. Roaring, he slams her into a wall and drags her along it. Pikachu comes to Samus's rescue, hitting the space dragon with a Thunder attack, after which the battle begins. Ridley fights similarly to Master Hand, using many brutal physical attacks. When he is defeated, he falls off the arena. Ridley is next fought in The Great Maze with any characters that have been rescued throughout the Subspace Emissary. He uses the same attacks and is defeated in the same fashion as before. Remixes of Ridley's theme music from various Metroid games can be optionally played in the Frigate Orpheon stage.

Super Smash Bros. for Wii U
In Super Smash Bros. for Wii U, Ridley is a stage hazard boss on the Pyrosphere stage. His physical appearance, like Samus's, is based on his appearance from Metroid: Other M. Once attacked enough by a player, Ridley allies with that player, and attacks the other players. He can also transform into Meta Ridley by absorbing enough energy. He can be defeated, and, as if he was a character, defeating him rewards the player with a K.O. point; he can be defeated by his own ally as well.

Super Smash Bros. Ultimate
In the upcoming Super Smash Bros. Ultimate, Ridley has been confirmed to become a playable character for the first time, announced during the E3 2018 Nintendo Direct. His appearance in this game seems to be based off of that in Super Metroid. His Final Smash involves him destroying Samus's Gunship.

Nintendo Land
In Nintendo Land, an animatronic Ridley appears as a recurring antagonist in the Metroid Blast attraction. Ice Ridley, a version of Ridley unique to this game, also appears.

Trivia

 * Ridley appears in Nintendo Monopoly, in which he takes the place of Tennessee Avenue. He costs $180.
 * Ridley's trophies in Brawl and Melee both state that he is the head of the Space Pirates on Zebes. This is false however, with the real head being Mother Brain.
 * Ridley's stock icon for Super Smash Bros. for Wii U uses his appearance from Super Smash Bros. Brawl, instead of his Metroid: Other M appearance.
 * Ridley's splash screen introduction in his Super Smash Bros. Ultimate reveal trailer; "Ridley Hits the Big Time!", may be a reference to "Ridley is Too Big", an internet meme originating from arguments against Ridley being a playable character in the Super Smash Bros. series.