That's the thing, Surtr is straight-up the end of all the worlds in Norse myth. He's prophesised to do it, and he does it. No ifs, ands or buts- no last destined hero, he isn't the villain of the piece to be defeated, he burns them all out, and then maybe burns himself out, and the whole world gets a fresher, more hopeful start. There's one sword that's said to be capable of stopping his, and that was one that was probably-maybe retconned in later, but was lost as a result of greed or pride or something in its own wielder's myth. I wouldn't put him up against megazord Galactus Zeus or anything, but any earthly god, I'd give Surtr an advantage at the very least.
The original one, that is, not the stupid bullshit corrupted version we got in the LB. I stand by the assertion that the edgy versions of all the characters are inferior, Edgecules and Jalter included.