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