Here is the full list of all 48 Persona 3 Reload achievements.
Rescued a missing person.
Spent an evening in the dorm with a teammate.
Used a total of 50 Twilight Fragments.
Defeated the Empress and Emperor.
Performed a fusion with three or more Personas.
Opened 50 treasure chests.
Obtained 10 Major Arcana during Shuffle Time.
Initiated 50 Chance Encounters.
Obtained an item from a Persona Conception.
Defeated the Priestess.
Triggered a skill change during fusion.
Performed 50 All-Out Attacks.
Obtained 10 Personas during Shuffle Time.
Defeated a rare, golden enemy.
Performed a Shift.
Performed a Dyad Fusion.
Joined the Specialized Extracurricular Execution Squad.
Obtained Orpheus.
Defeated the Hierophant and the Lovers.
Defeated the Chariot and Justice.
Defeated the Hermit.
Defeated Fortune and Strength.
Defeated the Hanged Man.
Sealed Nyx.
Watched the good ending.
Invited Elizabeth to your room.
Aced an exam.
Maxed out all Social Links.
Unlocked all Social Links.
Nurtured a romance.
Maxed out one Social Link.
Awakened all teammates' ultimate Personas.
Used all teammates' Theurgy.
Dealt over 999 damage in a single attack (All-Out Attacks excluded).
Discovered and conquered 10 Monad doors.
Encountered a Dark Zone in Tartarus.
Defeated the Reaper.
Fused Messiah.
Harvested a crop that you grew with a teammate.
Earned over a total of 50,000 yen from part-time jobs.
Maxed out one Social Stat.
Maxed out all Social Stats.
Ordered from a secret menu at the Iwatodai strip mall at night.
Nursed a cat back to full health.
Accepted an invitation to hang out five times.
Unlocked access to the remaining Major Arcana.
Unlocked a teammate's Combat Characteristic.
Acquired every Twilight Fragment in town.