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