What do you think Anti-Pinkie's backstory is? How do you think she got her cutie mark?
Please, be serious.

It's not pleasant, there's a reason I didn't include it in my Return to the Mirror Universe story.

So when the Rainboom flashed over the rock farm, both Pinkie and Anti-Pinkie instantly gained fourth wall awareness and physics defying abilities. As we know, Pinkie decided her one true purpose in life was making ponies and people laugh, and she saw the whole idea of being in a cartoon as funny. As her first act of fun she decided to throw a party for her family.

Anti-Pinkie or Pinkamena saw her existence as a cartoon as miserable, because she realized nothing she did actually mattered. She decided her purpose was to show ponies just how miserable their lives really were, and to spread anger and sadness among ponies. Her first act was to torture her family to the brink of death. To make it worse, during the torture she forced her mother to choose which of her siblings would take the most savage tortures, and essentially turned the whole family against each other in the most sick ways imaginable. The pie family, once a bastion of cheer and love (the opposite of Pinkie's unhappy boring family), is now a broken husk of itself. These mental scars are the reason why Mirror Maud lives a life of partying and became the virtue of good cheer... to try and escape her horrible past.

Pinkamena is a psychopath who feels no remorse for her actions, because she knows it's just a cartoon anyway. After she joined Mirror Twilight's mane six gang, Pinkamena often would subvert the group's missions to cause the most heartache and sadness to as many ponies as possible. For example she suggested poisoning Appleoosa's water supply to increase cider sales, and while it worked, it caused the residents alot of anger, sadness and pain, which Pinkamena observed with interest. It's important to note she doesn't feel joy at seeing others miserable, rather it gives her a sense of justification that existence is indeed as miserable as she views it. Lastly, Pinkamena views every problem in Equestria as the fault of humans (the writers) and therefore hates humanity utterly and completely, seeing us as a sick and twisted race.

Hope this answers your question.

5695447 5695535
That sounds almost like Dreadpool a Deadpool that literally try to destroy the fourth wall of the Marvel's multiverse by killing Marvel characters and eventually the characters that inspired the creation of Marvel's characters in the Ideaverse.
For those that don't know anything about the Dreadpool here a info link about here some videos of Dreadpool here.:

Now thinking about it that would make a interesting story a Pinkie Pie in alternative universe of Equestria got in a accident that made her fully able to see through the fourth wall and it drove her insane after realizing that her, her friends, her world are all fictional so Pinkie decide to end the the fictional world's suffering by destroying the world itself by killing off the world's characters both heroes and villiains alike.