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