I have to admit I know next to nothing about Kulak, Chthon is pretty beastly. Wasn't one of his spells when read out was capable of wiping out Asgard? (apologies if I am wrong there)
That was a weaker Spectre; golden age. But either way, Kulak was also more powerful than the Spectre in the bronze age in All-Star Squadron (which while chronologically takes place in that same era, it doesn't change the fact that in the same series Spectre's aura was powerful enough to nearly upset the multiversal cosmic balance iirc, and that was something like 10 issues after the Kulak story; it was in the 30s issues).
Chthon isn't that beastly really, although in that arc he was quite impressive. And he did banish Asgard (happened in Mighty Avengers); that was also at a time period when Thor possessed the OF (of course he wasn't on Odin's level); but nothing about that is more impressive than being above the Spectre.