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