Originally posted by Zentrex
Valk's showings are superior because he uses the force for attack and destruction, which is more quantifyable than using it for knowledge and defense, as Yoda does. But Yoda's hype pretty solidly puts him above Valkorion. Also, the fact that he was the unquestionable master of the Jedi at the height of the Jedi order + the fact that he was the grandmaster for close to a thousand years.
I see your point but you are giving too much weightage to sheer hype of a character which is not wise:
"I don't know for sure but I would imagine that there are no hard and fast lists about which Sith are the most powerful. "Most Powerful" would have lots of different variables to take into account. So it may be best to say that he was simply amongst the most powerful Sith along with Sidious and whoever else there may be. If you definitively say that one Sith was the most powerful then by definition any others that you create in the EU must be inferior so I doubt the continuity people make such absolutes about the powerfulness of the characters." - Leland Chee
Hype is a useful method to establish superiority of a character over others but one must watch out for outliers in an ever-expanding lore. Valkorion is an outlier by virtue of his evolution, sheer hype and showings.
Valkorion was able to replicate destructive power of superweapon Zildrog on Ziost, and he was preventing recovery of his homeworld Medriaas all along. A Republic fleet failed to stop him on Zioat. In-fact, entire Jedi Order and/or Sith Order of the time failed to save Ziost.
There are numerous ways to assess power of Valkorion including via scaling from other characters.
PT era Jedi Order hype is also contested in the lore: https://comicvine.gamespot.com/profile/darthant66/blog/knights-of-the-old-republic-era-is-the-prime-of-th/95277/
Disney's hype of Yoda is reasonable: https://www.starwars.com/databank/yoda
Yoda is stronger than most but not necessarily Valkorion TIER or even close.