UNICORNS. They build amazing cities, battle terrifying monsters, and... are super corruptible. Can you imagine keeping a world safe where a 3rd of the population has the ability to literally break time?
Starlight Glimmer, Sombra, Trixie with an Alicorn Amulet, Rarity with her evil inspiration spell, the corruptibility of unicorns is something that seems to happen freakishly often in Equestria. And it doesn't matter who it is either. One wrong spell, bad breakup, or fishy artifact and suddenly you have a super-powered magical creature wandering around causing all sorts of chaos.
How do we keep the unicorns from freaking out? Is it even possible? Are they the least safe pony race?