Shuma-Gorath could probably defeat Trigon on his own, even outside his dimension.
1) The Vishanti summoned the Living Tribunal to banish the Old One Slorioth because a direct confrontation would destroy the universe. Shuma-Gorath is said to be the Master of all the Old Ones, so would be stronger than Slorioth by default. Says a lot if he's master of one who could destroy the universe in a battle.
2) Made Sise-Neg near the end of his journey wary enough to avoid a direct confrontation with him.
3) Was one responsible for powering up the Cancerverse Galactus Engine that was handling Galactus + a number of Celestials. Was summoned in that same arc by Lord Mar-Vell in the ritual to try and kill 616 Death after it was said that entities larger and more powerful than the Cancerverse Galactus Engine were on their way. Hmm...
4) Allowed Doctor Strange to be galaxy buster level just with his mystical aura alone.
Enough evidence for me to say that Shuma-Gorath could deal with Trigon by himself and that Trigon certainly get past this entire team. Most appearances of Shuma-Gorath outside his dimension where we see him on panel have been him summoned at an iota of his power, yet from his past appearances he's still very powerful if he doesn't have some plot device weakening him.
Whether or not Sise-Neg recreated one universe in Marvel or all of them is irrelevant. It's clearly shown that he was drawing all the magical energy out of not just one universe, but all universes - EVERYWHERE. He sucked up the magical energy from Dr Strange and Baron Mordo while they were fighting in a void between universes.
That's why in this scan that says Sise-Neg held all extant power (all existing power)...
...we know it's not "all extant power from only ONE universe" as some like to say, because we saw Sise-Neg had already previously sucked up the power from Strange and Mordo while they were in a timeless void located outside the 616 reality. So "all extant power" can only be talking about all existing power from all of Marvel and not just a single reality within it.
Also, Sise-Neg did not just absorb all magical energy. It was all time and space. We clearly see that Sise-Neg's actions didn't just affect magical beings, but all matter and molecules as well. His presence almost causes Doctor Strange to fade away into nonexistence.
We also have this little doozy where the co-writer of the Sise-Neg arc states clearly that Sise-Neg became all-powerful at the end of his journey.
We had just completed Marvel Premiere #14-well, I had just completed the pencils, most of the art, but for some reason or another, nobody took notice of what we were doing. When the book came out, Stan finally got a hold of it, and I don’t know, somebody pointed it out, or he read it, and he wrote us a letter saying, “We can’t do God. You’re going to have to print in the letters column a retraction saying this is not ‘the’ God, this is just a god.” Steve and I said, “Oh, come on! ” So, Steve happened to be on his way to Texas for something, this is when we were in California, and we cooked up this plot-we wrote a letter from a Reverend Billingsley in Texas, a fictional person, saying that one of the children in his parish brought him the comic book, and he was astounded and thrilled by it, and he said, “Wow, this is the best comic book I’ve ever read.” And we signed it “Reverend so-and-so, Austin Texas”-and when Steve was in Texas, he mailed the letter so it had the proper postmark. Then, we got a phone call from Roy, and he said, “Hey, about that retraction, I’m going to send you a letter, and instead of the retraction, I want you to print this letter.” And it was our letter! We printed our letter!
@zorn_a_rust_red_scythe: Shuma can't drain all of Cyttorak's power, it will only continuously feed off of it indefinitely, but Cyttorak controls the power, since it is of Cyttork's essence, and not Shuma's. Essentially, Shuma will become the Juggernaut.
Shuma-Gorath was a threat to Sise-Neg because of his magic draining ability. That's enough evidence to say with certainty that his magic draining power would be too much for Cyttorak to handle. And as we see with Doctor Strange absorbing Arioch, entities with infinite power can be drained completely.
The Vishanti seemed to believe that they could eventually destroy Slorioth.
Long ago they fought Shuma-Gorath through unknown circumstances (I like to think they fought him while he was on Earth because Agamotto was Earth's original Sorcerer Supreme and Oshtur is an Elder God) and it doesn't seem like much came out of that. It seems like they gave up fighting Shuma-Gorath directly because they refused to help Doctor Strange in his struggle against him and Shuma-Gorath even tells Strange later that The Vishanti no longer concern themselves with him.
Shuma-Gorath, Master of the Old Ones, would come out on top. From Sise-Neg's hesitance to directly combat Shuma-Gorath for fear of losing energy, to making the Ancient One give up hope as soon as he learned S-G was targeting Earth, to severely weakening Gaea from his attack on Earth without even having to go there, I'd go as far as to say this battle would be easy for him. Probably a stomp considering Strange needed the uber Wings of Needless Sorrow, fusion with a chaos lord limited only by imagination, dark energy from Ghaszaszh Nyrih, and all of Victoria Bentley's magic potential just to combat Shuma-Gorath.
Zom has the fewest showings but I think he'd be in second just judging from having Dormammu and Eternity deal with him.