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