I actually take that back. With what we've seen her do, and given the fact that the only thing stopping OT Sidious from taking her planet to map the Kwa Infinity Gates there (Book of Sith) was the combined force of the Dathomirians along with her and her Nightsisters; I'd actually put her way above Exar Kun, and by a gargantuan margin.
While he probably was a large enough nexus at that point to destroy her 1 on 1, I doubt it wasn't as much her as it was the Rebellion consuming his military's time and resources - but still she is no match for Abeloth, who's dozens of times light side nexus FoTJ Luke.