The Royal Flush Gang was originally established as enemies of the Justice League early in their career. The team was comprised of an Ace Android, King of Spades, Queen of Spades, and Jack of Spades. This team was foiled by the League and the new hero - Technician. 
A new team of criminals, calling themselves "the Royal Flush Gang" took the mantle when the Crime Syndicate came to Earth and claimed to have killed the Justice League. Some members attended the Crime Syndicate's announcement in Happy Harbor. 
Members of the second wave of the gang included Ace of Diamonds, Ace of Hearts, a new King of Spades, Jack of Diamonds, Jack of Hearts, Jack of Clubs, and an army of numbered soldiers, one being an Eight of Hearts. The Royal Flush Gang was under the leadership of a new Ace of Spades.
Setting up in the "Man of Steal" casino in Atlantic City, New Jersey, the Royal Flush Gang caught wind of a bounty set on the Rogues' heads set by the Crime Syndicate themselves. Hoping to acquire more territory and power in exchange for the Rogues, the Ace of Spades sent the Diamonds division to track down and apprehend the Rogues in Gotham City. 
Though the Rogues escaped and killed the Diamonds, the Royal Flush Gang still had Golden Glider held captive as leverage. The Rogues then invaded the gang's territory, stole Glider back, and began fighting the army the Royal Flush Gang had at its disposal. The fight was interrupted by Johnny Quick and Atomica arriving, wanting to kill the Rogues themselves.
However, the Ace of Spades wouldn't give up the fight and shot Weather Wizard in the head with his shotgun anyway, seemingly killing him, and causing Johnny Quick to go into a fury, being robbed of his rightfully deserved kill. In a fit of revenge, Johnny Quick went around killing members of the gang until he was beamed back to the Watchtower to deal with an important issue. The second group of the Royal Flush Gang was rendered defunct. 
A third wave of criminals who became the Royal Flush Gang were active when Superman's identity was revealed publicly to be Clark Kent. The group was comprised of Ten, Jack, Queen, King, and Ace. This group didn't have a set card suit for each member, instead they wore a general collection of clubs, spades, hearts, and diamonds and referred to each other by their codenames.
The new Royal Flush Gang sought to bring grief to Kent by attacking his apartment building but happened to see him walking the streets on their way. Picking a fight, Ten only through one punch before Ace surrendered and started beating up King. The group were quickly arrested and lost their rights to the Royal Flush name. 
The fourth team to call themselves the Royal Flush Gang was active when Batman and Two-Face were on the hunt for a cure, all while having a bounty on their heads. This Royal Flush Gang attempted to get in on the action but missed their opportunity after the two men escaped the Beast.
Looking to pick up where the assassin had left off, the Royal Flush Gang asked the Beast for directions. However, all they received was a bomb on their hover board that killed them all, quickly ending their short career. 
- Ace Android: Though only used in some iterations, the group will sometimes make used of a hulking, white android as their "ace in the hole". 
- A giant playing card.
Weapons: None known.
- The Royal Flush Gang was created by Gardner Fox and Mike Sekowsky, first appearing in Justice League of America #43. However, in the rebooted Prime Earth continuity his first appearance as part of the DC Universe is in Joshua Williamson and Christian Duce's New 52 Craftsman Bolt-On System Saves the Justice League sponsored one-shot.
- No trivia.