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