The D&D equivalent to Godzilla is the Terrasque.
Sure - but its much smaller. And probably has a thinner neck.

The D&D equivalent to Godzilla is the Terrasque.
One word: Beholder.
So ... what happens when you crit a beholder with a vorpal sword, anyway?
A big, bald dead beholder on the ground and 10 really surprised eyestalks floating in mid-air?So ... what happens when you crit a beholder with a vorpal sword, anyway?
2) The PC slashes diagonally, then turns to face away from the enemy, sheathes his sword, and says something cool in Japanese. Then a moment later all the Beholder's eye stalks simultaneously fall off of the central eye, all with perfectly clean cuts severing them.
Not quite exactly and explicitly ten foot, but you get the idea:
So ... what happens when you crit a beholder with a vorpal sword, anyway?
Right up there with Denis Leary's undead headless Irishmen for ignoring vorpal weapons.
I fully endorse this option, although the one-liner need not be in Japanese, it could very well be said while doing a Schwarzenegger impression:
YouTube - 160 Greatest Arnold Schwarzenegger Quotes
More examples of these post-kill one-liners here