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