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