Secret Six

The Secret Six are a team of six individuals in DC Comics that have band together to achieve a common goal. While there have been heroic incarnations of the team, the Secret Six has mostly been associated with villainy.

Post-Crisis
After Lex Luthor learned that Alexander Luthor, Jr. formed the Secret Society of Super-Villains using his identity, he adopted the alias Mockingbird to gathered six criminals who also resented the organisation to help him stop the society's operations. Originally the team consisted of Scandal Savage, Rag Doll, Parademon, Deadshot, Cheshire and Fiddler, but after Fiddler was killed during their first mission, he was replaced by Catman. The Six Secret held their own against the secret society for a time, but the team eventually began to fall apart with the death of Parademon and the betrayal of Cheshire. Lex Luthor was soon exposed as Mockingbird and the teams remaining members left his services to continue as a mercenary group.

The Secret Six were hired to go on various missions together, losing and gaining members over time, until the group was spilt into two; one half run by Bane and the other half led by Scandal Savage. Scandal's team were soon recruited by Amanda Waller, posing as the new Mockingbird, who sends them on a mission that puts them into conflict with Bane's Secret Six.

New 52
During the New 52, a new Secret Six was formed after a number of villains were blackmailed by the Riddler, who adopted the Mockingbird alias. This version of the team was led by Catman and also consisted of Black Alice, Porcelain, Strix, Elongated Man (under the name Big Shot), and the third Ventriloquist (who eventually quits the team).

The Infected
As part of his plans to infect the world with Dark Matter, The Batman Who Laughs made his own unique version of the Secret Six by corrupting specific heroes using Batarangs tainted with a Dark Matter serum. Commissioner Gordon was already infected by the serum during a run-in with The Grim Knight while other members of the team included Shazam, Blue Beetle, Donna Troy, Hawkman, and Supergirl (although Superman was originally planned to be the final member).