Some of the antagonists could represent the 7 deadly sins.
Discord: Lust? Constantly striving for power and a proper paradise or relationship. Could also be sloth.
Trixie: Pride. OBIVOUS REASONS.
Queen Chrysalis: Envy. She feeds on love energy felt for someone else, and disguised herself as Cadance to become Shining Armor's wife. Kind of a loose-fitting one.
King Sombra: Wrath. Oppressed and threatened countless citizens, and is obviously filled with anger and hatred.
Tirek: Gluttony. Constantly fed on the magic and energy of citizens to grow more powerful. Could also be greed.
Storm King: Greed. Attempted to use Tempest to gain magic, as well as obtain a staff that acts as a conduit. He even exclaimed multiple times that the staff belonged to him.
Nightmare Moon: Sloth? She remained dormant for thousands of years, and remains so even still. Could also be lust, but I'm not sure how that would fit.
I dunno. Just a thought I had after watching the movie.