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