Here is the full list of all 45 Hogwarts Legacy achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Win the House Cup
Find the Map Chamber as a Slytherin
Find the Map Chamber as a Gryffindor
Find the Map Chamber as a Ravenclaw
Spend all Talent Points
Complete all collections
Complete all side quests
Reach Level 40
Complete all Merlin Trials
Reach a combo of 100
Find all Demiguise statues
Brew every type of potion
Unlock all Floo Flames
Discover all cairn dungeons
Breed every type of beast
Use Ancient Magic on every enemy in the game
Defeat enemies in all battle arenas
Complete Sebastian Sallow's relationship line
Complete Poppy Sweeting's relationship line
Defeat Ranrok
Complete Natsai Onai's relationship line
Subdue the Lord of the Shore
View all Pensieve memories
Upgrade a piece of gear 3 times
Rescue the phoenix
Wield a Deathly Hallow
Reach the highest point in the castle, the Headmaster's upper study
Beat Imelda's time in all broom races
Visit Poidsear Coast
Learn all spells
Save a dragon
Grow every type of plant
Stun 10 different enemies using a Mandrake
Defeat a total of fifty enemies using Petrificus Totalus
Use Flipendo ten times – to tip one cow or several
Upgrade a piece of gear
Complete all tiers of a challenge
Meet Charles Rookwood in the Map Chamber
Spend 5 Talent Points
Find the Map Chamber as a Hufflepuff
Follow butterflies to a treasure
Invoke Ancient Magic for the first time
Attend your first class
Survive the troll attack on Hogsmeade
Complete the introduction and finish the Sorting Ceremony