Here is the full list of all 79 Nioh: Complete Edition achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Used the mask of an ugly fellow to defeat an enemy.
Completed "The Ocean Roars Again."
Lit all three evil-warding bonfires in Itsukushima.
Forged an item.
Completed "Deep in the Shadows."
Bathed in first hot spring.
Reached level 10.
Completed "The Man with the Guardian Spirit".
You have unlocked all achievements!
Completed "The Demon of Mount Hiei."
Met with Tokugawa Ieyasu.
Witnessed Tokugawa's forces head toward a decisive battle.
Completed "The Source of Evil."
Completed "The Samurai from Sawayama."
Completed "The Demon King Revealed."
Completed "The Queen's Eyes."
Made two circuits around Japan.
Reached level 100.
Reached maximum proficiency with your first weapon.
Acquired mystic art for the sword.
Acquired mystic art for the dual swords.
Acquired mystic art for the spear.
Acquired mystic art for the axe.
Acquired mystic art for the kusarigama.
Acquired mystic art for Ninjutsu.
Acquired mystic art for Onmyo Magic.
Used a disguise.
Changed your hair style or beard.
Changed the appearance of an item.
Found Muramasa and brought him in.
Made a total of 60 requests at the blacksmith.
Collected all the best materials.
Completed 10 missions with NPC or in the “Yokai Realm with a companion” with other users.
Communicated with a yokai 10 times.
Confused an enemy for the first time.
Completed your first Twilight mission.
Obtained first divine item.
Defeated all types of yokai.
Bathed in every hot spring from the Kyushu Region to the Omi Region.
Acquired 40 gestures.
Collected all Kodama from the Kyushu Region to the Omi Region.
Collected all Guardian Spirits.
Became Ryunoshin the dung lover's best friend.
Collected all fragments of the Hiragumo teakettle from Shigisan.
Defeated the Nue of Mount Hiei.
Defeated Derrick the Executioner.
Completed "Yokai Country."
Completed "The One-Eyed Dragon's Castle."
Completed "Spirit Stone Huntress."
Collected all Kodama in the Tohoku region.
Acquired mystic art for the odachi.
Equipped +15 divine equipment in all slots. (Excludes accessories.)
Bathed in every hot spring in the Tohoku region.
Completed any mission while transformed into a woman.
Completed "Hands of the Dragon."
Seized all of Aoba Castle's three-storied keeps in "The One-Eyed Dragon's Castle."
Listened to Katakura Shigenaga's entire introduction in "The One-Eyed Dragon's Castle."
Completed the mission "The Siege of Osaka (Winter)."
Completed "Scion of Virtue."
Collected all Kodama in the "Siege of Osaka (Winter)" chapter.
Acquired mystic art for the tonfa.
Bathed in every hot spring in the "Siege of Osaka (Winter)" chapter.
Defeated Sarutobi Sasuke in the mission "The Siege of Osaka (Winter)" using only tonfa. (Cannot use a Visitor/Companion.)
Defeated Ganryu's Sasaki Kojiro using only Dual Wooden Swords. (Cannot use a Visitor/Companion.)
Used all the culverins in the mission "The Siege of Osaka (Winter)."
Defeated all of Sanada's Ten Braves in "Scion of Virtue."
Completed "The Sparrow Flies Again."
Equipped the Kusanagi Tsurugi, Yasakani Magatama, and Yata Mirror.
Completed "The Sanada's Resolve."
Completed "Resentment Unleashed."
Completed "The Last Samurai."
Bathed in every hot spring in the "Siege of Osaka (Summer)" chapter.
Collected all Kodama in the "Siege of Osaka (Summer)" chapter.
Completed "The Grand Tournament" on Way of the Strong or higher.
Completed "The Master Ninja" on Way of the Strong or higher.
Completed the 20th plane in The Abyss.
Destroyed all the destructible cannons in "The Sanada's Resolve."
Defeated the Onmoraki during "Resentment Unleashed."
Destroyed all the Revenant contraptions on "The Last Samurai."