>>107712027The HMC becoming villains could have been done much better.
Maybe at first they're willing to give Eclipsa a chance at being queen, with Omnitraxus being the most in favor and Heckapoo being the least. Then Mina attacks in her giant armor, and Eclipsa is forced to use the No Name Spell to stop her. Seeing the damage the spell causes sends her citizens into panic, and the HMC immediately act to remove her while Star tries to stop them.
Another way could have been that they, as Gloss' kids, are naturally tied to the realm of magic. The corruption of the realm begins to affect them, turning them evil and violent like the corrupted unicorns. They cause so much damage and are such a threat - near-unbreakable crystals, dimension hopping, and space-time manipulation will do that - that Star decides to destroy the magic realm to stop them.
With the magic destroyed, the HMC come to there senses in their final moments, and share one last hug as they fade away (Reynaldo gets to join in too. Maybe Glossaryk as well).