Just checking for who all counts in this:

Discord (despite being reformed)
Sombra
Chrystalis
Nightmare Moon
Sunset Shimmer

That covers our main villains, at this point, which leaves a couple of questionables like:

General changelings?
Actual monsters?
Garble and the other nasty dragons? Or do these all fall under "antagonists, not villains?"

3012303 I refuse to call Garble and the other dragons characters, let alone real villains. Changelings...I don't really know. Technically they are villains, but they were just following Chryssy's orders. If enough people request changelings, then I'll add a folder. Other monsters are in the same boat.

3012377
Wasn't Trix technically a villain with the amulet?

3012627 I thought about that, but in the end she wasn't really a bad pony. She just made some bad decisions.

3012648
Good point, but can we still ship villains with her? Such as Trixie x sunset?

3012678 Technically, yes, but the villain ships involving Trixie would have to go in the "Insert Villain x Other" folder.

3012303

For the sake of discussion, how are we defining "villain"?

Trixie played the role of antagonist twice, and Flim and Flam are set to reprise their role as antagonists.

Sunset Shimmer was arguably reformed at the end of Equestria Girls (although the sequel may state otherwise), and Discord, while antagonistic, is mostly reformed and harmless.

Suri Polomare remains unapologetic for her actions; Coco Pommel was the reformed one.

What about re-interpretations of previous generational antagonists like Tirek, Grogar, Bray, and The Smooze?