Often in the battle forums of Comicvine, threads discussing battles between abstract beings will throw around terms like "multiversal" and "omniversal"
I will acknowledge that comic books do have characters capable of destroying universes, like
However, many are referred to as ruling multiple universes without real data behind that
Now, i should mention that, for the most part, any one comic book universe will contain multiple "plains" or "dimensions", these include heavens, hells, places of fiction, and homes to unspeakable horror, but are still part of the same universe, more or less.
Confirmed, at the very least, for marvel cosmology http://en.wikipedia.org/wiki/Marvel_Universe#Dimensions
now, lets start with some characters
At the time Sandman was published (1989-1996) DC had already gone through a crisis that subverted and homogenized universal history, and only had one universe in the continuity. in addition to this, regarding the endless, Destruction states:
"The Endless are merely patterns. The Endless are ideas. The Endless are wave functions. The Endless are repeating motifs. The Endless are echoes of darkness, and nothing more...And even our existences are brief and bounded. None of us will last longer than this version of the Universe."
one could argue as to how well Destruction knew this, but he seems to know about the endless more than any other character, and it is more evidence to their presence in a single universe than i have ever heard of them being multiversal.
Now, i really don't have anything to say this guy isn't multiversal, but he has essentially no feats, people are afraid of him, but we don't really know why. There is no real material evidence that he is really even more powerful than people like Zeus or Ganthet in an objective sense.
Now, there is at least one alternate set of Vishanti in marvel, http://marvel.wikia.com/Vishanti_(Earth-791218) which would imply there are other versions in other universes, therefor the trio from 616 is not one who governs every universe, again, shady evidence, but more than you guys have than I've heard of them being multiversal beings
the comparison to the Celestials would imply that they have similar amounts of power.
Shuma Gorath is referenced as ruling thousands of "dimensions", (established as being separate from universes in marvel) and little in the way of "multiversal" power
he did appear as leader of the cancerverse, but seeing as a separate Hulk, Galactus, and Spider-Man appeared in the Cancerverse, it would not be an invcredibly large leap to say that it was also a different Shuma-Gorath
That being said, Shuma was banished by Crom, a Skyfather (and if Robert Howard is to be believed, an indifferent one) and he was able to banish Shuma from the cosmos, implying that Shuma's power, while probably greater than the average sky father, he can still be, at the very least, banished by one on neutral round
That being said, beings like Thundra and Arkon travel between universes, and are rarely said to be more powerful than being like Odiun of 616, who you have never seen enter another universe, so maybe counting universe isn't the same as comparing feats
If i have erred in my analyses, please inform me with some evidence that would refute my claims.
Also, no being can be truly omniversal, as universes are owned by different companies, many of whom hate each other.