Would of been an easy cover up tbh. "outlander killed blah blah, took Revenge etc" Pretty much what happened in story.
Revan had a good gauge on his power, Novel Revan is pretty reliable, when you have events like Nihilus draining Katarr it backs it. And yeah the majority of his power comes pre Novel.
Of course, he needed an extremely powerful vessel Nihilus was only an average force user to begin with, meaning he didn't midichlorian count or the ability to hold much energy(force power) in his body, thats
why he lost his Body, unlike Revan/Sidious those with enough Midichlorians/strength to hold energies within their bodies. Vitiate/Nihilus are just cases of their own power far exceeding their physical
limits.
Nathema is not comparable to Ziost/Katarr. Nathema literally stripped the force on the atomic level, over a planet. That requires a far more amount of energy than just, vaporizing/pulversing life/water.
Nihilus drain is a clear indication of Raw force power, as you need to strength to preform such a feat, no matter if it's a different drain.
did it say he achieved his old peak in power, or that he gained enough energy to beable to drain Ziost?
SOR Revan was stated by marr to be capable of wiping out the republic/imperial Combined Militaries by his lonesome, so its not that impressive.
So why as a spirit did Valkorian need to use Force lightning to weaken him before Force blasting him off the edge.Why not just one hit KO him again, oh wait he wasn't strong enough.
Tutamini's from a strong enough user. considering it's fired quickly I doubt,even in while used in his spirit form, as strong as his fully powered charged force lightning storm, as it doesn't require as
much raw power.