WE saw Valkorion's weakened spirit housed in an inferior vessel, electrocuting scores of military-grade warships (some really big) across the station while focused on Arcann. To the point that warship activity came to a complete halt. This is clearly fleet busting feat.
Now imagine what Valkorion would do to a fleet when in proper strength. There should be no doubts about Valkorion - he is SUPER in every category of Force Power. His choices are another matter.
I like the aspect of Valkorion being focused in his exploits, to minimize attention rather than leveling environments and boasting about his exploits on a frequent basis. Hall Hood have a similar viewpoint.
When Valkorion decided to devastate a WORLD to send a message across, he pulled it off with just a blast of power. He reduced every Force-user on the surface to dust in the process. And not any ordinary planet but a very big one with a massive populated base and multiple moons orbiting it.
Valkorion is without any doubt stronger than any individual Jedi or Sith.