Deathwing's gaping metal maw really personified Cataclysm as an expansion. His flying over zones and burning everything in his path to ash made him part of the world in a way that Illidan, Arthas, Kil'jaeden never managed. He combined the arrogance and sneering sense of superiority of a more human antagonist with the unfathomable menace and raw power of a destructive force of nature. He's the only raid boss to actually require two fights to finally defeat him.
I've always had a soft spot for ye olde Deathwing. I feel like we didn't get to see enough of his diabolical planning side, the schemer who manipulated the kings and princes of the Eastern Kingdoms into almost letting him take over Alterac and marry Calia Menethil. This was a plan with long-term aspirations and goals. We got to see a little more of his personality in the story Charge of the Aspects, but I would have liked to have seen more. Still, he's dead, the day has been saved, and we're moving on to those misty shores of Pandaria. But his legacy will live on.
Goodbye, Neltharion. Hopefully you rest quiet. You really were the Cataclysm.
World of Warcraft: Cataclysm has destroyed Azeroth as we know it; nothing is the same! In WoW Insider's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion, from leveling up a new goblin or worgen to breaking news and strategies on endgame play.