jimmyshilling notes that the achievement is incorrect. This is for 250 deaths. Thanks!
Also, HelpingOD notes in the comments that these must apparently be done in a single session.
In keeping with Sangriaz's solution here:
On party level 2, push both sticks to the right, then as they start falling, press
and
simultaneously to make all four blocks fall at the same time. And yes, all 4 count toward your total.
You can probably get a lot of this through natural gameplay, but at a tasty 100 GS for dying 999 times, I couldn't help myself but to blast through it faster.
Hope this helps!