While Persona (or Shin Megami Tensei games, in general) don’t incentivize the good ‘n old “gotta catch’em all” mentality for collecting all creatures, one might still be indulged by the possibility of obtaining all Personas available. But will they be rewarded for doing such a feat in Persona 3 Reload?
What Happens When You Get All Personas in Persona 3 Reload? (P3R)
As one may expect, yes. There is a special event for completing 100% of the Persona Compendium. Once you fuse your final Persona, leave the room and enter again. Elizabeth will comment on your astonishing progress.