Kun was as powerful as Nadd's spirit when he destroyed him, and screamed across the galaxy in triumph, so Exar Kun massively pre-prime can one-shot Sunrider with Telepathy, trap Arca Jeth in a Sith spell, control the minds of millions and turn the entirety of Onderon into an unusually powerful Dark Side nexus at whim.
Then Exar Kun became extremely powerful, using Sith Sorcery to unleash unchained raw power. Then he leaves to face Ulic, after which they both gain tremendous powers until they return several years later.
Kun, already the darkest power in the galaxy, kills Odan-Urr and takes the Dark Holocron, an object unrivalled among Sith Holocrons and which made him grow in power at an ever increasing rate until he became the most powerful Sith in history, far more powerful than even his apprentice.
So Exar Kun is so far above controlling millions and one shotting some of the most powerful Jedi of his day that these are basically low showings for him.
Caedus has nothing.