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.
Acquire all pyromancies.
Reach "The Usurpation of Fire" ending.
Acquire all sorceries.
Learn all gestures.
Reach "To Link the First Flame" ending.
Defeat Lothric, Younger Prince, Lord of Cinder.
Reinforce the Estus Flask to the highest level.
Discover Aldrich Faithful covenant.
Discover Mound-makers covenant.
Perform all forms of infusion.
Defeat Nameless King.
Defeat Champion Gundyr.
Reach the Untended Graves.
Discover Rosaria's Fingers covenant.
Discover Blade of the Darkmoon covenant.
Reinforce a bonfire to the highest level.
Defeat Dragonslayer Armour.
Reinforce any weapon to the highest level.
Defeat Ancient Wyvern.
Reach Archdragon Peak.
Defeat Old Demon King.
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 Pontiff Sulyvahn.
Discover Watchdogs of Farron covenant.
Discover Warrior of Sunlight covenant.
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 Way of Blue 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.
Reach "The End of Fire" ending.
Acquire all miracles.
Acquire all rings.