The Digital Mind Wave, or DMW, is an integral part of combat in Crisis Core Reunion. This is the slots in the upper left corner of the screen, that will automatically spin as soon as you enter combat. During battles, you will undoubtedly run into situations where the DMW will have the same image lined up on the left and right slots, which will force something called a Limit Verge. Should the third slot, in the center, match those other two, then you will be able to perform a Limit Break. In the PSP version of the game, these would be performed automatically, but in Reunion, they are stored instead. Upon gaining a Limit Break, you will have to press the Triangle (PS)/Y (Xbox)/X (Switch) button to actually perform the Limit Break. As soon as you perform your first one, then you will unlock this trophy/achievement. Unless you purposefully ignore this mechanic, then this should unlock naturally.