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