#1 Ronda Rousey
Ronda Rousey was the inaugural female Champion in UFC history after being awarded the Bantamweight Championship when she joined the company as the reigning Strikeforce Champion.
Rousey solidified her title reign with impressive victories over Liz Carmouche, Miesha Tate, Sara McMann, Alexis Davis, Cat Zingano and Beth Correira before upset losses versus Holly Holm and Amanda Nunes ended her MMA career.
After months of rumours, Rousey finally announced to the world that she had signed with WWE at the Royal Rumble on January 28, 2018, when she made a shock appearance at the conclusion of the first ever Women's Royal Rumble match.
From there the "Rowdy One" has not looked back. After the greatest ever debut in company history wherein, she teamed with Kurt Angle to decimate Triple H and Stephanie McMahon, Rousey would capture the Raw Women's Championship from Alexa Bliss in a one-sided battle at SummerSlam and retained the title against Bliss at Hell in a Cell, one month later.
Rousey continued to build her WWE legacy when she overcame the challenge of former Diva's Champion, Nikki Bella at the first ever all-female pay per view, Evolution on October 28. 2018.
The best is still to come for Rousey, with a bout against Becky Lynch on the horizon at Survivor Series as well as a rumoured Wrestlemania main event versus Charlotte Flair. Rousey is the best MMA Superstar that has made the successful transition to WWE already, just seven months into her WWE career.