The Super Villain

Villain is planning to destroy the world with their Big-Ass Space Weapon and is Mere Moments Away from doing so, but then something shows up. Something that's much worse than Villain and their weapon combined.

WTTV is a person
This newcomer quickly wipes out Villain or heavily damages them, properly replacing them and might have a different plan from Villain's or continues to do what Villain was about to but better and more efficiently. This can be because the newcomer thinks Villain Sucks (whether they heard of them before or not), I'm Better Than My Boss, or the newcomer just needs to be The Villain II.

WTTV isn't (exactly) a person
This could be a Giant Space Rock, Ancient Being, or Screw-Up In Spacetime that poses a larger threat than Villain could ever dream.