This video contains spoilers.

Smash TV
Break 11 test chamber monitors.

You can use your body, lazers, turrets, explosions and hard projectiles to break them.
There are 12 listed, however only the first 11 count, as I forgot that they had to be test chamber monitors, however, feel free to break it anyway.
These are all located in Chapter 8 - The Itch, starting from test chamber 1/19.