Sweetie Belle obtains the accursed Alicorn Amulet, and immediately becomes Ponyville's least feared super villain ever.
Not for lack of trying, of course.
It even has a YouTube reading! Check him out here.
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.