Here is the full list of all 34 Sekiro: Shadows Die Twice achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
All achievements have been unlocked.
Attained the "Return" ending
Attained the "Purification" ending
Defeated all bosses
Defeated "Great Shinobi - Owl" at the Hirata Estate
Defeated the "Demon of Hatred"
Defeated the "Great Colored Carp".
Upgraded all Prosthetic Tools to their limit
Used Lapis Lazuli to upgrade any tool to its limit
Attained the "Shura" ending
Defeated "Isshin Ashina"
Defeated the "Great Serpent".
Attained the "Immortal Severance" ending
Defeated "Sword Saint Isshin Ashina"
Defeated the "Divine Dragon" and obtained the "Divine Dragon's Tears"
Defeated the "Corrupted Monk"
Traveled to all areas of the game
Defeated "Great Shinobi - Owl"
Acquired all Ninjutsu Techniques
Used the Mortal Blade to sever the Guardian Ape's undying
Acquired all Prosthetic Tools
Defeated the "Guardian Ape"
Acquired all skills
Caught the Folding Screen Monkeys
Defeated "Genichiro Ashina"
Encountered the Memorial Mob
Fully upgraded the "Healing Gourd"
Defeated "Gyoubu Masataka Oniwa"
Defeated "Lady Butterfly"
Upgraded Vitality and Posture to their limit
Grasped the inner mysteries of any combat style
Returned from the dead using "Resurrection" for the first time
Acquired the Shinobi Prosthetic
Received the "Kusabimaru" from Kuro