That's where you're wrong. There are literally a dozen sources and accolades that put Palpatine and Vitiate as vastly superior beings to Nihilus.
His "raw power" was never demonstrated anywhere and frankly speaking, is a load of crap. He couldn't feed of the exile and yet for all his supposed power he couldn't even kill mandalore, a non force sensitive.
The arguments that fanboys make of him "holding his ship together" is another load of crap considering that when he dies the ship still stays in one piece, nothing but hyperbole.
Palpatine had the same ability to drain entire worlds and unlike Nihilus, whose power controls him, Palpatine has demonstrated the ability and control over planet wide force draining.
The old republic encyclopedia actually confirms that Vitiate is more powerful than Nihilus.
In fact, its never actually clear if Nihilus used a ritual in preperation for the devastation of Katarr considering that the origin comic of Nihilus was seen in the perspective of Visas Marr
Palpatine could summon gigantic wormholes on a whim that could do anything from ravaging an entire fleet of warships, to destroying the space time continuum and ravage entire worlds.
No one said it is, but people like yourself that constantly claim that only a wound in the force that can defeat Nihilus is complete and utter crap.
Luke skywalker, Count Dooku, Anakin Skywalker, Palpatine and several other characters have demonstrated the ability to remove themselves from the force and resist a planet wide drain(the dark reaper). The fallanasi people also have the same ability which is one concealed themselves from the Galactic Empire.
And that is exactly what is going to happen to him when he tries to feed on the characters that can remove their force connection/mask it from him.
You mean how he had to team up with Sion on a dark side nexus because he couldn't face Traya, a relatively powerful force user on his own? The fact that the KOTOR sourcebook guide specifically states that it was both Sion and Nihilus combined efforts that stripped Traya of the force?
Yep, he sure is powerful alright.
And there are plenty of powerhouses who can do more than just "resist" Nihilus.
Nihilus is very much beatable in conventional means. Anybody that knows the Fallanasi technique or have the ability to remove their force connection and Nihilus has no chance of severing their force connection or feeding on their force energies which would in turn get him weakened and allow a relatively skilled combatant to steamroll over him.