Extremely powerful

As is the case with most comic book characters because the comics are where things are truly highballed with powerscaling and cosmology.

By the end of this answer, you'll be blown away by how high Dr. Fate scales to with cosmology. Hopefully most people agree, so here we go:

Dr. Fate was able to fight Upsidedown man:

The Upsidedown man is described as the archetype of pure horror. He's an extremely powerful entity who was imprisoned by the Goddess Hectate:

The Upsidedown man draws power directly from the source, the source is the highest form of energy and it's been implied that Source = the Presence.

Dr. Fate blasted Upsidedown man with a fully powered energy blast:

Now this did not kill Upsidedown man and in fact Dr. Fate was knocked out after this event, but considering it did manage to hurt Upsidedown man says a lot.

Upsidedown man is capable of 4th wall breaking:

Dr. Fate has the capability of outright tearing apart the Sphere of the Gods:

Meaning the entire structure of the God sphere can be erased by Dr. Fate's efforts:

So how powerful of a feat is this? Where does the sphere of the Gods scale to cosmologically? Let me show you:

The God sphere holds platonic concepts and archetypes. DC writers were apparently big fans of Jungian's concept of archetypes and the collective unconscious.

True form Darkseid's mere shadow almost shattered the base multiverse:

Now keep in mind a shadow represents the absence of light, the absence of existence. So Darkseid's nonexistent form almost broke and shattered the multiverse.

The multiverse already contains infinite dimensional space and here's how:

Schrödinger's cat gets referenced a lot in DC comics:

Schrödinger's cat and the many worlds interpretation of quantum mechanics grants a type 3 multiverse. Type 3 multiverse is an infinite dimensional space.

Darkseid's shadow also aligns with Plato's cave drawing and explanation of how Platonic concepts work:

Meaning the Platonic concepts that reside in the God sphere are Outerversal.

Now the God sphere also contains an infinite number of realms within it:

Realms like Heaven which are the highest of the God sphere contain infinite layers:

Each heaven is described as a dream for individuals. The scan above states that there are higher more fundamental dreams meaning conceptual layers between dreams exists.

In the scan above, the Phantom Stranger also states that there are heavens beyond counting and there are heavens aka dreams that cross limits to the point where some leave the illusion of flesh behind. Proving that there are conceptual infinite layers of heaven.

This means that Dr. Fate can destroy the God sphere, a structure that holds true platonic concepts and Jungian archetypes. It also has an infinite number of heavens each one greater than the last with conceptual gaps.

More deeper information about the God sphere in this video:

Now for scaling Dr. Fate

Easily anywhere from Outerversal+ to High Outerversal (could get to Extraversal through the video above but I'm going with the safe scaling).