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