Destroy the purple speakers around Chronopolis.
Note that speakers re-appear in the world next time you play, but you only get credit for each location once. If you attack a speaker and it remains totally undamaged, then it's one you already got. Their locations are:
Avengers Mansion, right of the front door
On wall section in Sakaar, close to Nueva York
On the Nova Corps HQ in Xandar.
In the corner of a Medieval home.
On the Hala-facing side of Kang's spire
On the Egyptward side of Hydra Square
On the front facade of the palace in Wakanda (right where Shuri ends her rounds).
In downtown Manhattan, by a clockwise corner of the G-Cade building.
In Ancient Egypt, on the tomb nearest Manhattan Noir
In the Old West, underneath the geologically unlikely plateau which holds the town. Look just below the tumble weed inventor, and slightly upstream.
In Nueva York, near the top of the under-level access closest to England.
In Attilan, on a hubside under-level wall. If the main walkway is noon, it's at about 4 o'clock.
In Hala, in the archway just below the billboard there.
In Manhattan Noir, on one of the shorter apartment buildings toward the sea and the Brooklyn Bridge.
In Asgard, on rocky spar just clockwise from the Bifrost bridge, on the mainland.
Destroying them all unlocks Taserface's M-Ship, but you never get to hear about the bee in Kang's room again.