BarbarousFlash 
Nightmare version are usually their core idea pushed to the extreme though? Basically their worst selves. Luna is eternal night driven by jealously, that one time Daybreaker appeared she seemed to be firey arrogance, and Nightmare Rarity was just Rarity turned up to 11. So instead of Divorce, a Nightmare Cadance would be all the unhealthy aspects of love. The sort of controlling and manipulative love that’s extremely abusive.
