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