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