I've seen several mentions of World Of Warcraft dragons already, but you're all forgetting the most baddass of all the dragons in that game: The Black Dragonflight, particularly Neltharion aka Deathwing and his three children; Nefarian, Onyxia and Wrathion.
Now, Deathwing was the dragon aspect of earth and a pretty cool guy until the Old Gods (WoW's Lovecraft knock-offs, in case you couldn't tell) drove him insane by playing What Does The Fox Say non-stop in his head. When this happens his blood turns to fucking magma and he goes around doing all kinds of evil shit, like making the super-evil Dragon Soul artifact and kicking the crap out of Malygos's brood.
This is all before WoW. During the first two expansions Deathwing is hiding in the elemental plane of earth, because it turns out having fucking lava for blood is not good for you, even if you are a dragon. Thankfully, the batshit crazy Twilight's Hammer cult is on hand to fix him up, making an epic suit of armor for him out of Elementium. Deathwing then burst out of the plane of earth and into Azeroth, knocking the elements out of whack and basically ruining everyone's day. WoW loses tons of subscribers as players flee in terror from Deathwing's wrath (or it may have been because Cataclysm was just a really shit expansion).
Deathwing is only beaten by travelling back in time, stealing his super-evil dragon soul from the past, and charging it with the power of the other dragon aspects, then using on its own creator. Thrall gets to help too because he's Chris Metzen's favourite character. He fires a freaking massive lazor at Deathwing, but his armor deflects it! So everyone gets on a airship and chases him, parachuting onto his back to peel off his armor. Deathwing is so evil, even his blood is evil, attacking you as you destroy the armor. Thrall fires again and this time scores a direct hit, Deathwing crashes into the Maelstrom, a massive fucking whirlpool at the centre of the world. Everyone is patting Thrall on the back when Deathwing comes out of the maelstrom, a molten gribbly mass of awful nasty evil. Everyone gets to work on his limbs so he can be flushed down the maelstrom like some gross spider. Thrall, not wanting to miss an opportunity to steal the spotlight, Thrall tries the dragon soul again, and promptly makes Deathwing fucking explode. Epic dragon, shame about the expansion he was in. More on the Black Dragonflight later!