I don't know if you know what personality types (MBTI) are, but Fluttershy is an ISFP type: Introvert Sensing Feeling Perceiving.



Her opposite is ENTJ: Extravert Intuitive Thinking Judging.



She's letting that dark twisted distorted ENTJ inner side out under extreme stress. The form the creators of the show chose was interesting. She becomes a bully of all things.



Research this if you want, but...



Pinkie Pie is ESFP with INTJ inner opposite.

Rarity is ENFJ with ISTP inner opposite.

Twilight Sparkle is INTJ with ESFP inner opposite.

Applejack is ESTJ with INFP inner opposite.

Rainbow Dash is ESTP with INFJ inner opposite.



It'd be great to see this all explored so much further.