Here is the full list of all 43 DARK SOULS III achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Complete all achievements.
Learn all gestures.
Acquire all rings.
Perform all forms of infusion.
Reach "The End of Fire" ending.
Reach "The Usurpation of Fire" ending.
Acquire all sorceries.
Acquire all miracles.
Discover Mound-makers covenant.
Acquire all pyromancies.
Reach "To Link the First Flame" ending.
Defeat Lothric, Younger Prince, Lord of Cinder.
Defeat Champion Gundyr.
Reinforce the Estus Flask to the highest level.
Reinforce a bonfire to the highest level.
Defeat Old Demon King.
Defeat Nameless King.
Defeat Ancient Wyvern.
Reach Archdragon Peak.
Defeat Dragonslayer Armour.
Reinforce any weapon to the highest level.
Reach the Untended Graves.
Defeat Oceiros, the Consumed King.
Defeat Dancer of the Boreal Valley.
Defeat Aldrich, Devourer of Gods, Lord of Cinder.
Discover Rosaria's Fingers covenant.
Discover Blade of the Darkmoon covenant.
Discover Aldrich Faithful covenant.
Defeat Pontiff Sulyvahn.
Defeat Yhorm the Giant, Lord of Cinder.
Defeat the Deacons of the Deep.
Defeat Crystal Sage.
Discover Watchdogs of Farron covenant.
Defeat High Lord Wolnir.
Defeat the Abyss Watchers, Lords of Cinder.
Defeat the Curse-rotted Greatwood.
Discover Blue Sentinels covenant.
Discover Warrior of Sunlight covenant.
Defeat Vordt of the Boreal Valley.
Discover Way of Blue covenant.
Become a Host of Embers for the first time.
Defeat Iudex Gundyr.
Light a bonfire flame for the first time.