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.
Equipped +15 divine equipment in all slots. (Excludes accessories.)
Defeated the Onmoraki during "Resentment Unleashed."
Completed "The Sparrow Flies Again."
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.
Completed 10 missions with NPC or in the “Yokai Realm with a companion” with other users.
Completed "The Last Samurai."
Collected all Guardian Spirits.
Defeated all types of yokai.
Destroyed all the Revenant contraptions on "The Last Samurai."
Collected all Kodama in the "Siege of Osaka (Summer)" chapter.
Completed "Resentment Unleashed."
Completed "The Sanada's Resolve."
Completed "Scion of Virtue."
Collected all Kodama in the "Siege of Osaka (Winter)" chapter.
Defeated all of Sanada's Ten Braves in "Scion of Virtue."
Completed the mission "The Siege of Osaka (Winter)."
Completed "Hands of the Dragon."
Collected all Kodama in the Tohoku region.
Acquired mystic art for the spear.
Completed "Spirit Stone Huntress."
Completed "The One-Eyed Dragon's Castle."
Listened to Katakura Shigenaga's entire introduction in "The One-Eyed Dragon's Castle."
Seized all of Aoba Castle's three-storied keeps in "The One-Eyed Dragon's Castle."
Completed "Yokai Country."
Collected all the best materials.
Collected all Kodama from the Kyushu Region to the Omi Region.
Communicated with a yokai 10 times.
Became Ryunoshin the dung lover's best friend.
Changed the appearance of an item.
Used the mask of an ugly fellow to defeat an enemy.
Made a total of 60 requests at the blacksmith.
Acquired mystic art for Ninjutsu.
Made two circuits around Japan.
Completed "The Queen's Eyes."
Defeated Derrick the Executioner.
Completed "The Demon King Revealed."
Obtained first divine item.
Completed "The Samurai from Sawayama."
Acquired mystic art for Onmyo Magic.
Reached level 100.
Completed "The Source of Evil."
Acquired mystic art for the sword.
Confused an enemy for the first time.
Witnessed Tokugawa's forces head toward a decisive battle.
Found Muramasa and brought him in.
Met with Tokugawa Ieyasu.
Reached maximum proficiency with your first weapon.
Completed "The Demon of Mount Hiei."
Defeated the Nue of Mount Hiei.
Completed your first Twilight mission.
Collected all fragments of the Hiragumo teakettle from Shigisan.
Completed "The Ocean Roars Again."
Lit all three evil-warding bonfires in Itsukushima.
Changed your hair style or beard.
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!
Acquired mystic art for the dual swords.
Acquired mystic art for the axe.
Acquired mystic art for the kusarigama.
Used a disguise.
Bathed in every hot spring from the Kyushu Region to the Omi Region.
Acquired 40 gestures.
Acquired mystic art for the odachi.
Bathed in every hot spring in the Tohoku region.
Completed any mission while transformed into a woman.
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)."
Equipped the Kusanagi Tsurugi, Yasakani Magatama, and Yata Mirror.
Bathed in every hot spring in the "Siege of Osaka (Summer)" chapter.
Destroyed all the destructible cannons in "The Sanada's Resolve."