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