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