Their only hope would be Thanos, Drax, and Maxam distracting Surtur long enough for Warlock to use the Soul Gem on him. Still, I would give this to Surtur 7-8/10.
I don't see the Soul Gem being that useful against Surtr. It Karmic Blast Thor or Herc very well, and we've never seen a Soul Rip against a being of that nature.
I think their best bet is having Maxxam punch Drax in the gut and then handing the Power Gem off to Thanos.
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...You are Number Six. Respect Popeye
He was able to do whup up on big M because M's realm and power were comprised of all M's captured souls. I don't think Muspelheim would be similar, assuming that's even ewhere they'd be battling.
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...You are Number Six. Respect Popeye
Thor destroyed the IW except for Thanos. And gave Thanos fits when he had the PG.
Surtur owns Thor. Surtur is demonstrably a galaxy destroying power. The IW's only chance here is to give all 6 gems to Thanos and even if he cannot form the IG at least he can use many of their powers at the same time.
Unless Odin is restraining Surtur which he does all the time otherwise Surtur would be out vaping everything, Surtur owns the IW. Surtur is beyond any skyfather short of Odin or PC Darkseid.
__________________ Among the tales of sorrow and of ruin that come down to us from the darkness of those days there are yet some in which amid weeping there is joy and under the shadow of death light that endures.
J.R.R. Tolkien, "Of Beren and Luthien" from the Silmarilion