The evil reign of one filly in particular is drawing near, and Ponyville must once again face the terrible and terrifying wrath of Sweetie Belle. Now, it's up to Rarity to stop the not-so-greatest threat in Equestria in time for dinner, or the world will be doomed!
Or... not.
Most likely not.
Sweetie Belle obtains the Alicorn Amulet and tries to be evil for a day. She isn't very good at it.
The Great And Evil Sweetie Belle returns with a vengeance as the least threatening villain in Equestria.
Sweetie Belle takes a trip to Canterlot with her sister. Now she rules everything. The royal guards are thoroughly baffled.
Sweetie Belle sells her soul to a demon in exchange for very evil powers, and proceeds to (fail to) take over Ponyville.