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