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.
Collected all Kodama in the "Siege of Osaka (Summer)" chapter.
Collected all Kodama in the "Siege of Osaka (Winter)" chapter.
Made a total of 60 requests at the blacksmith.
Bathed in every hot spring in the "Siege of Osaka (Summer)" chapter.
Bathed in every hot spring in the "Siege of Osaka (Winter)" chapter.
Completed "The Master Ninja" on Way of the Strong or higher.
Completed "The Grand Tournament" on Way of the Strong or higher.
Defeated all of Sanada's Ten Braves in "Scion of Virtue."
Defeated all types of yokai.
Completed "The Last Samurai."
Collected all Guardian Spirits.
Destroyed all the Revenant contraptions on "The Last Samurai."
Completed "Resentment Unleashed."
Defeated the Onmoraki during "Resentment Unleashed."
Collected all Kodama in the Tohoku region.
Seized all of Aoba Castle's three-storied keeps in "The One-Eyed Dragon's Castle."
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.)
Destroyed all the destructible cannons in "The Sanada's Resolve."
Completed "The Sanada's Resolve."
Completed "The Sparrow Flies Again."
Completed "Hands of the Dragon."
Completed "Scion of Virtue."
Used all the culverins in the mission "The Siege of Osaka (Winter)."
Completed the mission "The Siege of Osaka (Winter)."
Completed "Spirit Stone Huntress."
Completed "The One-Eyed Dragon's Castle."
Bathed in every hot spring in the Tohoku region.
Listened to Katakura Shigenaga's entire introduction in "The One-Eyed Dragon's Castle."
Completed 10 missions with NPC or in the “Yokai Realm with a companion” with other users.
Completed "Yokai Country."
Made two circuits around Japan.
Completed "The Queen's Eyes."
Defeated Derrick the Executioner.
Lit all three evil-warding bonfires in Itsukushima.
Became Ryunoshin the dung lover's best friend.
Collected all the best materials.
Bathed in every hot spring from the Kyushu Region to the Omi Region.
Completed any mission while transformed into a woman.
Used a disguise.
Used the mask of an ugly fellow to defeat an enemy.
Acquired mystic art for Onmyo Magic.
Acquired 40 gestures.
Acquired mystic art for Ninjutsu.
Acquired mystic art for the axe.
Acquired mystic art for the kusarigama.
Acquired mystic art for the tonfa.
Acquired mystic art for the spear.
Acquired mystic art for the dual swords.
Completed "The Demon King Revealed."
Obtained first divine item.
Completed "The Samurai from Sawayama."
Acquired mystic art for the sword.
Reached level 100.
Completed "The Source of Evil."
Acquired mystic art for the odachi.
Reached maximum proficiency with your first weapon.
Witnessed Tokugawa's forces head toward a decisive battle.
Met with Tokugawa Ieyasu.
Found Muramasa and brought him in.
Completed "The Demon of Mount Hiei."
Defeated the Nue of Mount Hiei.
Communicated with a yokai 10 times.
Completed your first Twilight mission.
Collected all fragments of the Hiragumo teakettle from Shigisan.
Changed your hair style or beard.
Forged an item.
Confused an enemy for the first time.
Completed "The Ocean Roars Again."
Changed the appearance of 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!
Collected all Kodama from the Kyushu Region to the Omi Region.
Equipped +15 divine equipment in all slots. (Excludes accessories.)
Equipped the Kusanagi Tsurugi, Yasakani Magatama, and Yata Mirror.
Completed the 20th plane in The Abyss.