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