Here is the full list of all 86 Ato achievements.
Beat Ato on Accessible Difficulty
Beat Ato on Experienced Difficulty
Defeated Demon
Obtain all scrolls
Collect EVERYTHING
Once obtained, Successfuly perform the counter ability on an enemy
Collect all runes
Defeated Leader
Defeated Berserker
Max out your magic meter
Defeated Vagrant
Cut 50 stalks of bamboo
Completed Armor Arena
Defeated Turtle
Destroy 50 wall crystals
Obtain all talismans
Completed Fatal Arena
Defeated Champ
Defeated Blameless
Collect all coins
Defeated Archer
Collect a magic bar
Defeated Tiny Warrior
Perform the legendary move on an enemy
Defeated Tempest
Completed Throw Arena
Defeated Cross Blade
Defeated Monk
Defeated Samurai
Defeated Deceiver
Defeated Father Statue
Defeated Sentinel
Completed Spin Arena
Defeated Daggerman
Defeated Phantom Shin
Defeated Warden
Defeated Warden without the vision upgrade
Defeated Shadow Jin
Defeated Yari
Defeated Child Statue
Warp from one gate to another
Defeated Geisha
Defeated Ancient Warrior
Jump 1000 Times
Defeated Mother Statue
Equip a Rune
Obtain your first Rune
Defeated Twins
Defeated Bandit
Destroy a blue crystal block
Defeated Acolyte
Defeated Ninja
Defeated Guardian
Hit opponent 5 times while they are launched
Obtain your first Coin
Defeated Jin
Parry your opponent
Increase your max health
Obtain your first Talisman
Defeated Rogue
Defeat The Leader without killing his servants
Perform the just-frame legendary move
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