After reading one of the threads on here about "Hardest Bosses in WoW" or whatnot, I've been seeing many people posting that C'thun pre-nerf was impossible.
Sadly, I started playing WoW just before BC was released, and only managed to get to the mid 40s by the time BC was released; therefore, did not see any Vanilla raiding.
Anyone care to explain why a fight is being called "impossible"? That word isn't thrown around a lot on these forums, so I'm intrigued.