I disagree. The Whispering Death is the most badass.
Its wings rotate. Its sword-sharp teeth rotate. It has the greatest jaw strength of all dragons and can tunnel through all kinds of rock - though it can't tear through steel or higher metals.
It breathes fire. It shoots spikes. It is unaffected by the Thunder Drum's roar and thus can most likely survive the boneknapper's as well. It can't walk but it can dig-dig-dig and fly both at high speeds. It digs faster, but still.
Its only weakness is sunlight - but that simply distracts it. The sunlight doesn't burn it or anything.
As part of the boulder class, it can cause pretty much everyone to die from just hitting them. It's also incredibly large. Even though it can't walk, it can crawl like a snake.
It's not my favorite dragon and my fav can definitely defeat it. But it's still the most badass.