Going by what DC has published ...
Generally speaking, withIN the DC multiverse, the Presence gets top billing. However, two things about The Presence: He was only able to stalemate the Great Evil Beast (who utterly stomped the Spectre). And then there's this exchange between Him and Lucifer Morningstar ...
So, in His own words ... not truly omnipotent or eternal.
Beyond the Presence, there's the Primal Monitor aka the Overvoid, to whom the entire multiverse was like raindrop is to the ocean (making this Primal Monitor the same level of being as Marvel's pre-retcon Beyonder).
However, this Monitor has no usable feats beyond caging the entire multiverse to study it.
Finally, beyond the Primal Monitor, there is The Writer, DC's equivalent to Marvel's The One Above All. Like TOAA, The Writer is the in-story avatar of the publisher, who wrote the DC multiverse onto the unwilling Primal Monitor as its paper.
The Writer (there looking like Grant Morrison) is fiction-busting level and stands alone.
Those are your top 3 DC "characters" (or plot devices).
FWIW, Thought Robot Superman and the new cosmic being Perpetua are likely just below the Presence.