Here is the full list of all 48 Persona 3 Reload achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Maxed out all Social Links.
Watched the good ending.
Sealed Nyx.
Unlocked all Social Links.
Fused Messiah.
Defeated the Reaper.
Awakened all teammates' ultimate Personas.
Invited Elizabeth to your room.
Defeated the Hanged Man.
Encountered a Dark Zone in Tartarus.
Defeated Fortune and Strength.
Maxed out all Social Stats.
Nurtured a romance.
Acquired every Twilight Fragment in town.
Defeated the Hermit.
Used all teammates' Theurgy.
Discovered and conquered 10 Monad doors.
Defeated the Chariot and Justice.
Maxed out one Social Stat.
Aced an exam.
Unlocked a teammate's Combat Characteristic.
Nursed a cat back to full health.
Unlocked access to the remaining Major Arcana.
Dealt over 999 damage in a single attack (All-Out Attacks excluded).
Defeated the Hierophant and the Lovers.
Earned over a total of 50,000 yen from part-time jobs.
Harvested a crop that you grew with a teammate.
Rescued a missing person.
Maxed out one Social Link.
Spent an evening in the dorm with a teammate.
Triggered a skill change during fusion.
Obtained 10 Major Arcana during Shuffle Time.
Used a total of 50 Twilight Fragments.
Defeated the Empress and Emperor.
Ordered from a secret menu at the Iwatodai strip mall at night.
Accepted an invitation to hang out five times.
Initiated 50 Chance Encounters.
Defeated a rare, golden enemy.
Performed 50 All-Out Attacks.
Obtained an item from a Persona Conception.
Performed a fusion with three or more Personas.
Opened 50 treasure chests.
Defeated the Priestess.
Obtained 10 Personas during Shuffle Time.
Performed a Shift.
Performed a Dyad Fusion.
Joined the Specialized Extracurricular Execution Squad.
Obtained Orpheus.