Discord: Regular third-wheel

Sombra: Mexican who enslaves

Chrysalis: Overly obsessed anti-lover

Nightmare Moon: Death of the party

Tirek: MLP Herobrine

Trixie: Envious over-achiever

Sunset Shimmer: Twilight's human-world replacement

Starlight Glimmer: First tries to create a cult where everybody is equal, no pun intended, then ends up as presumably 7th pony element, but 8th if you count Sunset

Midnight Sparkle: Main heroine becomes a villain in 3rd human spin-off movie

Diamond Tiara: . . . Use your imagination

Flutterbat: I thought she was so adorable, well-planned, and epic looking, that I had to put her on this list as a villain.

Princess Celestia: Let's see, where should I start?

. . . Villains in a nutshell.