Who is the enemy of Cthulhu?

Hastur
Hastur (The Unspeakable One, The King in Yellow, Him Who Is Not to be Named, Assatur, Xastur, H’aaztre, or Kaiwan) is an entity of the Cthulhu Mythos….

Hastur
First appearance	“Haïta the Shepherd”
Created by	Ambrose Bierce
In-universe information
Species	Great Old One

Is anything more powerful than Azathoth?

Azathoth (Cthullu Mythos) is the strongest being in whole fiction. Because all the fiction and reality both are in his dreams including suggsverse and other Omnipotent being like The One Above All. However, Azathoth (Demonbane) is weaker than The One Above All.

Can Azathoth and SCP-682 fight each other?

This would just result in an endless paradox as Azathoth doesn’t fight and remains sleeping as SCP-682 does its thing. I don’t think either can slay each other.

Would SCP-682 be able to beat Deep Ones?

Deep Ones are a hardy bunch, impervious to old age, but not immortal to physical damage. So SCP-682 would definitely win against a good amount of Deep Ones. Mi-Go are interdimensional insectlike entities that can survive in space. But as the Deep Ones they’re not impervious to physical damage, so SCP-682 would fare well against these too.

Does Azathoth have a supreme form?

This evidence suggests that Azathoth has a supreme form in a mild manner but has no proof of having supreme almighty power. So it might be invincible, but not to the point of being eternal. Meanwhile, SCP-682 or Atanti-ql-Paneu is an unstoppable Leviathan birthed from the Scarlet King, whose might varies and is difficult to quantify.

How powerful would Azathoth be compared to atanti?

This makes it a hyperdimensional/extradimensional being in offensive capabilities. This can make Atanti relative to the Outer-Gods of the Lovecraftian Mythos. Azathoth shouldn’t be more powerful than all of the Outer-Gods combined, in fact, it should only be a little bit more powerful than Yog-Sothoth.