#4 Shayna Baszler
From a pure fighting standpoint, there are few superstars who could believably beat Ronda Rousey. She is one of the most decorated female fighters in the history of the UFC, and is often dubbed 'the baddest woman on the planet' by the WWE.
Step forward, Shayna Baszler. Rousey's fellow MMA horsewomen is one of the meanest superstars currently employed by the WWE, and while her MMA record may not be quite as dominant as Rousey's, she would still make for an incredibly believable victor against the current Raw Women's Champion.
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From a booking perspective, this one manages itself. While the two women have been allies on WWE television so far, there is nothing stopping Baszler debuting and taking out Rousey, laying claim to her 'baddest woman on the planet' moniker in the process.