Who do you think fits this bill?
As much as I love the Sith, they do have a very weighty advantage over Jedi currently, as do a lot of droids, assassins and bounty hunters. Basically half of the dark characters have some sort of anti Jedi ability.
I see why Anti Sith is rare, next to none if any from the movie universe can claim to be Sith killing experts, chances are the devs will need to pull from the old republic universe.
Though I suppose prequel Kenobi is reasonably close, two Sith dismemberments, one dead droid, and, well, didn't die against Dooku twice lol. Yoda possibly?