Here is the full list of all 86 Ato achievements.
Max out your magic meter
Defeated Vagrant
Completed Armor Arena
Defeated Turtle
Completed Fatal Arena
Defeated Champ
Defeated Blameless
Collect all coins
Obtain all talismans
Defeated Archer
Completed Spin Arena
Defeated Daggerman
Defeated Sentinel
Collect all runes
Defeated Shadow Jin
Collect a magic bar
Defeated Tiny Warrior
Perform the legendary move on an enemy
Hit opponent 5 times while they are launched
Defeated Warden
Defeated Warden without the vision upgrade
Beat Ato on Accessible Difficulty
Beat Ato on Experienced Difficulty
Defeated Demon
Defeated Leader
Defeated Samurai
Defeated Bandit
Defeated Phantom Shin
Completed Throw Arena
Defeated Cross Blade
Defeated Tempest
Defeated Geisha
Defeated Monk
Defeated Deceiver
Defeated Father Statue
Defeated Twins
Equip a Rune
Obtain your first Rune
Defeated Berserker
Jump 1000 Times
Defeated Yari
Defeated Child Statue
Defeated Ancient Warrior
Defeated Mother Statue
Warp from one gate to another
Destroy a blue crystal block
Defeated Acolyte
Defeated Ninja
Obtain your first Coin
Defeated Guardian
Defeated Jin
Parry your opponent
Increase your max health
Obtain your first Talisman
Defeated Rogue
Defeat The Leader without killing his servants
Once obtained, Successfuly perform the counter ability on an enemy
Perform the just-frame legendary move
Obtain all scrolls
Collect EVERYTHING
Destroy 50 wall crystals
Cut 50 stalks of bamboo
Beat Ato on Bushido Difficulty
Beat the first 3 bosses on Hell Difficulty
Beat Ato on One Hit Difficulty Mode
Beat Ato without collecting a Rune
Beat Ato without obtaining a dodge ability
Beat Ato without collecting Talismans, Coins, Runes nor extra Magic
Beat Ato in 2 Hours