How do I force-STOP something?

I was organizing my fonts, and I accidentally opened a BUNCH of windows (720 to be exact)... and there they went!

All of them, animated opening, one on top of one another. Bam bam bam bam... Eventually my machine locked up 😟

I tried
CMD - .
CMD - ESC
ESC
CMD - W
and all combinations of the above...

and NOTHING would stop the insanity... in case this happens again, is there a key combo to HALT something?

If not, there should be.

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