The OP says it all. It’s for a throw-away line in a story I’m working on. Prepfably it would be a roughly humanoid cbeast, but “fiery” and “giant” are more It should definitely be a malevolent entity; I cannot use the words dragon, phoenix, or surtur. If you name a creature from a workof fiction rather than myth, it has to be from a story published pre-1987, as that is when the story is set, and I’m relating thoughts of a specific character.
Thoughts?
Balrog?
Salamander.
Jötunn or Logi.
I thought of Balrog right after I hit submit. It would be perfect were it not so associated with Professor Tolkien. I’m going to look around and see if I can find legendary antecedents the professor might have drawn on; if anybody knows some (other than Surtur), I’d be grateful to hear about them.
Can’t use that one for in-story reasons. Besides, they aren’t giants.
Fire Elemental
Pit Fiend (Wall of Fire at will*)
Chimera (+ a dragon head)
*why yes, I am a roleplayer 
I’ve already used jotun and jinn in the sentence in question. I’m basically trying to ditch the word “dragon.”
If anyone has a suggestion on a mythological giant stone beast, I could use that instead. (But not troll; I’m thinking BIG. Kaiju big. Big enough so that it could reasonably be in the same attack group as a roc.)
Bob?
“Bob, the giant malevolent fiery humanoid beast who ate McKeesport, PA” has a nice ring to it.
Stone Golem
Earth Elemental
You know that blather I’m always skiting about superman and paying and all that crap? Pretend I wrote it here.
Agni?
Oh, all right. Call it a Meassë.
That’s a JRRT name for a very bloodthirsty Vala, who got edited out of the Silmarillion.
Ifrit.
For some reason i recall that’s a fire based thing. Then again, i got it from Final Fantasy. But I believe it’s older than that.
Too close to jinn.
ETA: You edited while I was posting, so I’ll append. In Arabic legend, ifrits are akin to jinn. See the wikipedia article, which I am too lazy to link too.
Xolotl is the Aztec god of fire and bad luck.
What’s wrong with just “fire giant?” They were a perfectly respectable race of fire-based gigantic humanoids in Norse mythology, destined to war against the gods and destroy Midgard in the time of Ragnarok. Alternately, if “fire giant” isn’t glamorous enough for the purpose, what about the Norse “eldjotun” (plural: “eldjotnar”)?
Volcanor, a terror-inducing giant made from molten lava. He’d kick Godzilla’s ass*.
*On land, at least. It wouldn’t function so well at sea.
Well, giant salamander then, you picky bastidge. 