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