#10 Kharma
Granted, this "flop" was less of a booking faux-pas and more of a series of unfortunate events.
Kharma was signed to WWE in December 2010 to much hype. Prior to her signing, she had been tearing it up in TNA and on the independent scene as Amazing/Awesome Kong, and WWE fans yearned to see her break Divas in half.
And for a while, she did.
Debuting at Extreme Rules in May of 2011, Kharma made an instant impact by demolishing a departing Michelle McCool with the Implant Buster. For the next few weeks, she went on a tear, attacking former WWE Divas Champions on both RAW and SmackDown. This was, until the May 25th edition of RAW, when she interrupted a tag team match, only this time, it wasn't to attack anybody. Instead, the monstrous "Diva" fell to her knees and broke down crying. The next week, she announced that she was pregnant and needed to take a leave of absence.
Not an ideal start.
Kharma would end up wrestling only one match in WWE - the 2012 Royal Rumble match. Though she did manage to toss Hunico out, she was eliminated by Dolph Ziggler after just one minute. So Kharma, one of the most world-renowned women's wrestlers in the world, only wrestled for a literal minute in WWE before being released in July of 2012.
To make matters worse, she sadly revealed in March of 2012 that she had miscarried the previous December. This is likely the reason why she never made another appearance in WWE. She was in no place to continue wrestling.
Truly saddening.