[Boromir88]

Galin, already mentioned this, lets not mix two different periods of time here where Tolkien began altering and changing his Balrogs.

I know the Balrogs were of the Maiar, but it seems unbelievable that a mere high elf like Ecthelion and Glorfindel could've slain them (more unbelievable is Echthelion who was able to slay 3 Balrogs)~Gorthaur

I think this is where the 'unbelievability' is coming from. As when Tolkien first started writing about his Balrogs, they were an entire race of their own. There were 'armies' and 'hosts' of Balrogs and they were much weaker than what the Tolkien's 'final' Balrogs became.

I don't know when Tolkien decided to switch things around, but eventually he made the Balrogs corrupted Maiar and as Galin remarks reduces their number down to at the very most...seven (HoME X: Morgoth's Ring; Myths Transformed).

So, the time you are talking about when Ecthelion slew 3 of them, was an earlier time when Tolkien had the idea that the Balrogs were an entire race of their own (not Maiar) and therefor far less powerful. That might be where part of the 'unbelievability' is coming from, because I agree that it would be unbelievable for any elf to slay 3 Maiar!

However, it's not so unbelievable that an Elf could take down a Balrog. Tolkien wrote a story where the lines of 'power' always mix and mingle together and there is no clear 'hierarchy' of who is more powerful. And we have to remember when we generally say that 'Elves are more powerful than Men' that doesn't mean we can assume that every elf is more powerful than every man. Just as I dont think one can assume every Maiar is equal in power, and every Balrog was equal in power. Just keep that in mind too, we're not dealing with a strict, rigid 'hierarchy of power,' but one that is just all meshed together. That is why Elves end up slaying Maiar, and Hobbits end up doing serious damage to a giant kick butt spider...etc.

Lets also not forget that Ecthelion and Glorfindel are extremely powerful Elves in their own right. They were Noldor Elven Lords, not your simple ordinary elf. They had also both seen the light of the two trees, and any elf who did, we are told grew in power.

Now if a Man slew a Balrog (even a 'great man' such as Turin) I would say that is 'unbelievable.' As it appears to take more than being a skilled and powerful fighter to slay a Balrog. Gandalf was locked in a 10 day battle with Durin's Bane and there was more than two foes who were crossing swords (or in this case one with a whip and the other with a sword):

'Long I fell, and he fell with me. His fire was about me. I was burned. Then we plunged into the deep water and all was dark...'

'We fought far under the living earth, where time is not counted. Ever he clutched me, and ever I hewed him...'

and...

'Out he sprang, and even as I came behind, he burst into new flame. There was none to see, or perhaps in after ages songs would still be sung of the Battle of the Peak.' Suddenly Gandalf laughed. 'But what would they say in song? Those that looked up from afar thought that the mountain was crowned with storm. Thunder they heard, and lightning, they said, smote upon Celebdil, and leaped back broken into tongues of fire. Is not that enough?'

(All quotes come from The White Rider).

This was a 10-day struggle amongst two Maiar. And as Gandalf says to the Fellowship 'This is a beyond any of you.' (Aragorn and Boromir are no chumps when it comes to 'fighters' amongst mortals). Gandalf was already weary, however in this case he could use his full Maiar powers. Gandalf was just restricted from showing his true form/powers when there were Elves and Men around...well here he's battling a Balrog under and on top of mountains. There is no one around to see it, and as I think is clear from Gandalf's description, he let loose his Maiar abilities in this great 'Battle of the Peak.'

I guess the bottomline here I'm trying to get at, is it's not so unbelievable for some of the most powerful Elves around (Glorfindel and Ecthelion) to slay a Balrog...as these two chaps were right up there in that 'greatest elf' category. However, if a mortal slew a balrog, than I would say that is rather unbelievable, because I think it takes a certain power that mortals don't possess.