Persona 5 Tactica

This achievement is unmissable, as the ability to fuse Personas is one of the trademarks of the Persona franchise and P5 Tactica is no exception to this signature gameplay trait. You'll be introduced to this feature after you complete Mission 8 in the main campaign (where you defeat Ann/Panther to progress). Continue along until you get to a cutscene where you reacquaint with Lavenza in the Velvet Room, where she'll introduce you to the concept of Persona fusions. You'll have four Personas from which you must choose 2 to complete a fusion. You'll also need to equip at least one of your party members with these Personas as your sub-Persona whose skills will be available alongside those of your main Persona before you can exit the Velvet Room menu. Once that's done, the achievement should pop-up after the following cutscene is complete and you return to the safehouse menu.