Principal Cinch is the main antagonist of My Little Pony: Equestria Girls: Friendship Games and the unseen overarching antagonist of My Little Pony Equestria Girls: Legend of Everfree. She hates sharing the victory with others and aims to prove that her school is better.
Her cold treatment is what causes Sci-Twi's transformation into Midnight Sparkle. This is what causes all of her students to turn against her and, as a result, Cinch is fired from her job.