Oh shit, and the Exile too.
Characters like Brand come in below Luke and co. as having had roles that weren't irreplaceable. Luke and Anakin accomplished things that frankly no other character could have replicated.
Meanwhile, someone like Vitiate was influential in the sense that the existence of his empire for so many years constitutes an influence unto itself, but he really accomplished nothing in the long run.
Valkorion:-
01. Nathema event (creation of a permanent void in the Cosmic Force)
02. Reconstituting the ancient Sith Empire
03. Orchestrating the Mandalorian Wars
04. Orchestrating the Jedi Civil War (result: Republic on its knees and the Jedi 0Order almost extinguished)
05. Great Galactic War
06. Children
07. Establishing a new superpower (The Eternal Empire)
08. Reducing Ziost to a barren wasteland
09. The Eternal Empire brought both the Republic and the ancient Sith Empire to their knees
10. Forging the Outlander as a weapon against The Eternal Empire
In the nutshell, Valkorion affected countless and was responsible for the deaths of countless as well.