
Doflamingo's ultimate last move vs. Luffy's King Kong Gun.
Doflamingo: ''16 holy bullets!''

He was talking about ''national treasure'' in Marijoa before:

Doflamingo believes, he can probably take Imu down with Law's Ope Ope no Mi, or perhaps switch bodies with Imu, who knows.

So Imu either is the national treasure of Marejoia or she controls it.
Per Doffy, this is a power that can "control the world itself".
@comrade.