While Ronda Rousey was dominating the Ultimate Fighting Championship and being heralded as one of the world’s best athletes, a handful of naysayers maintained that someone else was actually the best fighter in women’s mixed martial arts.

On Saturday, that woman, Cristiane Justino, known as Cyborg, will finally make her U.F.C. debut.

Justino, a 30-year-old Brazilian, has dominated opponent after opponent, winning titles in the Strikeforce and Invicta promotions. Like Rousey, she has won many of her fights in a matter of seconds. Unlike Rousey, whose specialty is the armbar, Justino tends to send opponents to the canvas with a devastating knockout punch.

But she has never fought in the U.F.C., largely because of weight class issues. Justino fights at 145 pounds, while the U.F.C.’s heaviest weight class for women, in which Rousey fights, is 135 pounds. Justino, who is 5 feet 8 inches, has been reluctant to cut weight to get to that level.

Fighting in different promotions did not stop Rousey and Justino from engaging in a long-running war of words. Justino called Rousey and U.F.C. officials bullies, while Rousey ripped Justino for testing positive for steroids after a fight in 2011.