Sunset Shimmer

Sunset Shimmer is the main antagonist in My Little Pony: Equestria Girls.

Personality
Throughout the first film, Sunset Shimmer is shown to be mean, short-tempered, greedy, bratty, egotistical, cruel, condescending, manipulative, and dishonest. She frequently insults and belittles others, and thinks little of it. According to human Fluttershy, Sunset makes life miserable for "anyone who stands in her way". As a result, much of the Canterlot High student body is afraid of her. She is also shown to be mainly concerned with gaining power, desperately trying various attempts to get Twilight Sparkle's crown in order to use its magic.

However, she doesn't appear to be willing enough to inflict physical pain on others, or at least not upon small animals (i.e. Spike), claiming she isn't a monster. Despite this, she appears to be easily irritated when someone else is praised in her presence, to the point of being provoked into attacking them.

When Sunset puts on the element of magic, she transforms into a demonic visage of herself. While in this form, she becomes more fierce and goes so far as attempting to dispose of Twilight. After she is defeated by the Elements of Harmony, Sunset Shimmer becomes immediately repentant and apologizes for her actions, appearing to renounce her prior dishonest and unkind ways.

Backstory
Sunset's backstory is explored deeper in the comics. Here, it is shown she had a very troubled relationship with her mentor Princess Celestia, which explains her descent into evil (though she was already extremely arrogant, self-centered, and antisocial, thus her mentor's short patience with her). Sunset had previously appeared in the form of a toy and as a NPC in the MLP Gameloft game. In both versions, she was merely a neutral character and not a truly evil one.

Trivia

 * Sunset Shimmer will become Pooh's enemy but reformed in the end of Pooh's Adventures of My Little Pony: Equestria Girls.
 * Sunset Shimmer will become the FT Squad's enemy but reformed in the end of The FT Squad's Adventures in My Little Pony: Equestria Girls.
 * Sunset Shimmer will become Thomas' enemy but reformed in the end of in Thomas' Adventures of My Little Pony: Equestria Girls and becomes Thomas and Twilight's new friend in Thomas' Adventures of My Little Pony: Equestria Girls - Rainbow Rocks.
 * Sunset Shimmer will become Brian's enemy but reformed in the end of in Brian Griffin's Adventures of My Little Pony: Equestria Girls but turns evil again at the end of Brian Griffin's Adventures of My Little Pony: Equestria Girls - Rainbow Rocks.
 * Sunset Shimmer will guest star in Hiatt Grey and Stuingtion's films Pooh and Brian Griffin's Adventures of Transformers: Age of Extinction and Brian Griffin vs. The Mummy: Tomb of the Dragon Warrior be back at her evil self, join forces with Trixie to get revenge on Twilight and try to kill her.
 * Sunset Shimmer will become G-merl's girlfriend while she's reformed in Emerl's Adventures Of My Little Pony Equestria Girls: Rainbow Rocks.
 * Sunset Shimmer Transformed into an Alicorn in The Night to Remember.
 * Sunset Shimmer will remain as a villain in Hiatt Grey's Series.
 * Sunset Shimmer turns good in the fictional movie: Princess Twivine Rises! and then leaves into the world.
 * Sunset Shimmer will be guest starring in Feddie's films: Thomas and Twilight Sparkle's Adventures of Wallace and Gromit: The Curse of the Were-Rabbit, Thomas and Twilight Sparkle's Adventures of Disney's Villains' Revenge, Thomas and Twilight Sparkle in Fantasmic (Walt Disney World Version), Thomas and Twilight Sparkle's Adventures of the Thief and the Cobbler and Thomas and Twilight Sparkle's Adventures Chronicles helping any friend in need.
 * Sunset Shimmer will appear in Pooh's Adventures of The Harry Hill Movie as a reformed character and she along with Abu, Harry's pet Hamster will be joining Pooh ands his friends at the end of the film.