[Lalwendë]

Originally Posted by Boromir88

Aragorn is ignorant of the nature and history of Balrogs, his reaction to stand with Gandalf was because the sense to not let Gandalf "stand alone" was greater than any fear he might have felt.

I still have this niggling feeling that Aragorn knew what was in there while Gandalf did not, given his words to him before they decide to go through Moria.

Fastforward to the bridge. Gandalf decided to challenge Durin's Bane again. "I am a servant of the Secret Fire. Wielder of the flame of Anor..." (Bridge of Khazad-dum). Gandalf isn't just uttering nonsense here, he is revealing his true nature as a Maiar and servant of Eru. Once knowing Durin's Bane was indeed a Balrog, Gandalf understands their nature and history, thus knowing no one else in the Fellowship had the will, weapons, nor skill to defeat him. The Balrog answers the challenge by "stepping onto the bridge."

Gandalf is possibly the only person in Middle-earth with enough power to hope to battle this Balrog. He has been sent there by the Valar and he carries their blessing. I also suspect that he may be the only one of all the Istari to be capable of this - note that he specifies 'fire' here and we know he uses fire and light (and Light) on many occasions. He is also known to arrive with the dawn, as at Helm's Deep and Anor is the Sun. A perfect opposition to creatures such as Balrogs who are part darkness (or Unlight).

Galadriel apart (Glorfindel is a matter of huge speculation), none of the others are considered particularly puissant in matters of conflict. Gandalf is an embodied Maia WITH a ring of power. Eladan and Elrohir whilst of note, have a standing closer to a Dunedain than say Echthelion.

Galadriel should be possessed of power to deal with the Balrog, and I don't see how she could not know it was there, not far from her borders, however the crucial point I think in why Gandalf is particularly able to handle it is that he has the blessing of the Valar. Galdriel does not. She is still at that point somewhat under a cloud.

Tolkien was constantly altering and rewriting his Legendarium. Glorfindel was the one and the same as the Balrog killer of Gondolin.

Fighting the Balrog would not be needless and I never implied the Wise would fight him alone. Just like when they attacked and drove off Sauron it would be a combined effort. The White Council that drove the Necromance, even if Sauron desired, out of Mirkwood would defeat the Balrog.

Glorfindel is another possible suitable opponent, yes. However again, I think that what he does not possess is the blessing of the Valar.

As to why the White Council did not deal with the Balrog, it's a moot point as to whether they knew it was there. There was something that had scared the Dwarves away, but who would be willing to find out? And even if they knew, it was likely that they chose to leave it well alone - it had frightened the Dwarves out of one of their strongholds and what is that in comparison to the threat that Sauron had faced and would face to all of Middle-earth?