The most powerful enemies in WoW

[Rince]

this is true but dont forget ony isnt resistant to FR damage and rag will no doubt spawn his adds to physically attack ony, she cant kill them all at once!

depending on who hits harder a physical fight would be interesting to say the least

Sry to disappoint you, but Ony is immune to fire :P

[Mahir]

apparently so, hm, ok then physical it is and adds, this would make a very interesting fight indeed.

[Falgorn]

Ragnaros doesn't seem that upwardly mobile, so I'm thinking Ony is going to have to hit up his lair if she wants to pick a fight. Lets presume she manages to move out of the group on Baron and makes it down to Ragnaros she is still short a whole lair full of eggs... Does she even get a phase 2...? Roof space is minimal in Molten Core...

Lets safely say that the most powerful enemy in WoW is the group who manage to 5 man the last 40 man raid boss in the game 12 months after the last expansion much to the frustration of casual gamers everywhere, still getting their 100th atunement key to the first instance of the second last expansion, whilst trying to save up 1 million dol.. gold for their own draenai space ship mount.

Either that or Blizzard will end it all by creating a giant unkillable Murlock to Torment us all into WoW 2 - aka World of Warcraft, jump to Lightspeed

[Juju]

Now you're thinking too much, I'm not saying the place wouldn't matter, but the fight doesn't have to happen where we fight them in the game, in fact it probable wouldn't (not that we'll ever see that fight...), but I'd say Ony wins, as for Blackwing, he owns Rag big time regardless of where the fight happens.
I'm not sure Ony's immune to fire, but she de"finitly has a rather high resist to it. Seems to me that a fight between let's say nightmare and prince in kara would be more interesting ;-)