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