The following idea was inspired by this thread.

It's pretty much been established by now that Sunset Shimmer is the bearer of the Element of Empathy, if not in-universe then confirmed by the artists, writers, and animators of the show, right? Meaning she can feel the emotions of others. What if, after so much exposure to negative emotions (hatred from those who believe her to be Anon-A-Miss, betrayal from her friends, etc) combined with her own negative emotions (confusion, sorrow, betrayal, hopelessness, etc.), her Element becomes corrupted?

Now, instead of allowing Sunset to sense the emotions of others, her Element leaves her emotionally dead inside, leaving her pretty much running on auto-pilot? What if her corrupted Element also produces an aura that directs the negative emotions of others away from her, specifically towards others? If this aura weakens positive emotions (joy becomes amusement, love becomes a crush, etc.) while strengthening negative emotions (irritation becomes hate, sadness becomes sorrow, anger becomes rage, etc.)? What if this aura kept increasing in strength and size with each passing day?

It would be a race against time for Twilight to try and solve this greatest of friendship problems, for with emotions riding high already and the aura becoming stronger every single day, CHS is a proverbial powder keg, and all it would take is on tiny spark to ignite a school-wide, perhaps even city-wide, tragedy.