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