Fury Heart, AKA Mare-do-Wrong, is an Artificial Alicorn from Equestria. Once being a Pegasus who idolized Rainbow Dash in her club, she was once a nerdy child when Rainbow Dash first moved into Ponyville on her birthday. Since she rescued her from danger on her fifth day, she wanted to be just like her. However, as she spent time in the Club, she started to notice all the bad things she did on the side like in Read It And Weep and Tanks for the Memories, she thought of her as a joke, and thus renounced her as her idol, and left to be a magical crime lord who tricked someone into giving her a Unicorn horn and turning into a 'renegade Alicorn', and manages to trick a misinterpreting Onyx Luck into believing Rainbow Dash to be a criminal, and that she "murdered" Mare-do-Well out of jealousy. But when this proves to backfire, she'll take the identity 'Mare-do-Wrong' and prove to be a challenge as the two will settle their differences and return her ill-gotten horn back to it's original owner. She has a costume similar to Mare-do-Well, but a coloration similar to Nega-Duck.
- "I was in a different place back then! All I wanted to do was be just like you! A hero! A Wonderbolt! Heck, an INSPIRATION!!! Then I watched as you were involved in wrongful act after wrongful act! Theft of a book from a hospital! Attempted industrial sabotage of a season! Heck, even the silly fanfictions of you, like Double Rainboom, OR, most disgusting of all, Rainbow F*****g Factory, paints you in a deplorable light, cause even if they're not canon, the idea of them still, BUGS ME! And every time, Equestria just FORGAVE YOU! Heck, even the Wonderbolts are a joke! Not only was Wind Rider a bastard, but the Wonderbolts were incompetent d***wads who oppress with nicknames, leave their own members in the dust, and worst of all, ACCUSE YOU OF A CRIME WITHOUT PROPER INVESTIGATION! And after ALL that, you still decided to just STICK AROUND!!! You're NOTHING but one big epic fail! And this time, things will be different! You're going to pay, for my name is not, Fury Heart! Or... Perhaps you can call me... (He dons a Mare-Do-Well costume with a Negaduck coloration)... MARE-DO-WRONG! (Cackles)..... (Raindow and the others stared unimpressed.)..... Yes, I know, the Name was TOO predictable, just, roll with it, it's my first time as a super villain, okay? Sheesh! Everyone's a fucking critic!"