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