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