Star Wars: All Sith/Dark Side Users/Allies (Canon)
A list of all Sith, Dark Side users or important people allied to the Dark Side ever introduced in Star Wars Canon through the films, books, comics etc.
Spoilers for all media, including major spoilers for Jedi: Survivor
Order is done in timeline order but goes by characters first chronological appearence
Needs an update for the Obi-Wan Kenobi series, which introduced the Fourth Sister and Third Sister/Reva. If you're including Sith who are mentioned by name but not seen (which it seems you are, given that you have Plagueis's first appearance listed as Ep. III) then a recent novel also mentioned Revan by name.