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