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