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