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