Here is the full list of all 53 Persona 5 Royal achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Unlocked all achievements.
Watched the ending.
Completed every Palace.
Visited a temple.
Passed time at the fishing pond.
Evolved a party member's Persona.
Completed Mementos.
Maxed out all social stats.
Completed the cruise ship Palace.
Entered a special relationship.
Ordered from the special menu at the maid café.
Completed the casino Palace.
Attended the jazz club.
Completely changed the cognition of Mementos.
Scored the highest on your exams.
Completed the spaceport Palace.
Scored a prize in the crane game.
Customized a gun.
Completed the pyramid Palace.
Couldn't take the heat in the bathhouse.
Played a game of billiards.
Performed a Gallows execution.
Performed an execution during a Fusion Alarm.
Maxed out one of your Confidants.
Completed the bank Palace.
Sold old clothing at Furugi no Neuchi.
Played a game of darts.
Performed a Showtime attack.
Obtained a Treasure Demon.
Encountered a deviation in Mementos.
Completed the museum Palace.
Performed a Group Guillotine execution.
Used Incense on a Persona in Lockdown.
Went to a hangout spot with someone.
Performed an Electric Chair execution.
Triggered a Technical.
Performed a Guillotine execution.
Traded in stamps while in Mementos.
Conquered the Reaper.
Traded in flowers while in Mementos.
Obtained a Skill Accessory from a Palace ruler.
Completed a Mementos request.
Defeated enemies via Disaster Shadow explosion.
Established your own squad of thieves.
Completed the castle Palace.
Won the lottery.
Cleaned up in Leblanc.
Scored a hit at the batting cages.
Worked a part-time job.
Performed a Baton Pass.
Used the grappling hook.
Obtained a Persona through negotiation.
Obtained Arsène.