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