Could be a minor/major school villain, teaching the lesson of how people dig their own grave, so to speak. ... Ah, there are so many other facets and potential subplots in this.
The thought was inspired by watching this little crossover again:
P.S.: Somewhat related crossover comic of mine: http://dowlphin.deviantart.com/art/How-Dan-managed-to-abduct-Rarity-412825674