You can't. There is no stopping it.
5 seconds sound clip from the The Avengers (2012) movie soundboard.
You can hear this line at 01:43:54 in the Blu-ray version of the movie.
Quote context
[...]
- And there's one other person you pissed off...
- Loki! Turn off the Tesseract, or I'll destroy it.
- You can't. There is no stopping it.
- Stark, we're on your three, headed northeast.
- What? Did you stop for drive-through?
- Swing up Park. I'm going to lay them out for you.
[...]