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