Rokk and Sorban
Rokk and Sorban
Intergalactic gamblers from the planet Ventura who square off with Superman - and later Batman - at the gaming tables.
First, the duo bet that they can force Superman to kill someone (he doesn't - he tricks them) (S No. 171, Aug 1964: "Superman's Sacrifice!").
In an adventure with Batman, as he gambles for Batman's life and the Earth's fate, Superman bests the luckless duo in a game of skill and chance (WF No. 150, Aug 1964: "The Super-Gamble with Doom").
In an cruel gambit, Rokk and Sorban create duplicates of Jor-El and Lara, merely to wager whether Superman would kill them on finding his "parents" to be actually evil (Act No. 582, Aug 1986: "The Strange Re-Birth of Jor-El and Lara!").
Also, these unapologetic wagerers are responsible for the second race between Superman and the Flash (chronicled in The Flash No. 175, Dec 1967: "Race to the End of the Universe").