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