Nephthys
The Gr8est!!!!!!!!
You're missing alot of the more esoteric stuff he does with the various extensions of himself and also the fact that he can use the light side and can use the Force in places like Nathema which imo counts as a special skill.
You're also being incredibly generous to Palpatine while ignoring a lot of stuff for Valkorion. Stuff you gave Palpatine but missed from Valk:
-Force Blast
-Pure Dark Side Energy Manipulation
-Dark Side Burst
-Force Corruption
-Force Sense
-Precognition
-Force Meld
-Force Visions
-Mental Shielding
-Mind Trick
-Mind Domination
-Force Shield
-Force Augmentation
-Alter Environment
-Dark Healing
A bunch of the remaining things are basic stuff that he obviously knows like Beast Control, Force Fear and Detoxify poison.
Also it's almost without mention that Palps has appeared in a hundred times as much content as Valk has and a good portion of Valkorions claim to fame is that he spent 1400 years studying the darkside and other force practices.