Full list of all 84 LEGO Harry Potter Collection achievements worth 2,000 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox One.
Achievements they've won
Achievements they've not won
Defeat every Harry freeplay variant as Lord Voldemort
Complete the game to 100% (Single Player Only)
Unlock all of the members of Dumbledore's Army (Single Player Only)
Unlock every character with a pet (Single Player Only)
Unlock all witch characters (Single Player Only)
Unlock ALL of the Order of the Phoenix character variants (Single Player Only)
Unlock every bad wizard (Single Player Only)
Complete the Bonus Level
Complete "The Flaw in the Plan"
Complete Year 8
Complete "Snape's Tears"
Defeat Bellatrix with Neville (Waiter) in a duel
Collect 1 billion studs (Single Player Only)
Complete "Just Desserts"
Complete "Out of Retirement"
Use a Weasley box with every Weasley
Complete "Fiendfyre Frenzy"
Complete "Burning Bridges"
Defeat 30 Red Caps
Unlock every pyjama character variant (Single Player Only)
Defeat Bellatrix as any Sirius Black character variant in a duel
Visit the Hogwarts Foyer in Year 7/8
Use a Quibbler dispenser 25 times
Complete "Back to School"
Complete the scene where Hermione and Harry dance in the tent
Unlocked on hitting 50% game completion (Single Player Only)
Complete "The Thief's Downfall"
Complete Year 7
Complete "Lovegood's Lunacy"
Complete "Sword and Locket"
Complete "In Grave Danger"
Complete "Magic is Might"
Complete all lessons (Single Player Only)
Complete "The Seven Harrys"
Use the Deluminator
Complete "Horcrux and the Hand"
Complete Year 6
Complete "Felix Felicis"
Complete "Love Hurts"
Complete "A Not So Merry Christmas"
Complete Year 5
Complete "A Veiled Threat"
Complete "A Giant Virtuoso"
Complete "Kreacher Discomforts"
Complete "Dumbledore's Army"
Complete "Dark Times"
Complete all the LEGO Builder tutorial levels.
Destroy 50 Devil's Snare plants
Defeat 10 enemies with a Muggle character
Hide in a barrel as Snape
Defeat Harry (as Voldemort), in the Graveyard
Defeat Quirrell in the Quirrell boss fight, using Voldemort
Complete the game to 100%
Buy every version of Voldemort (Quirrell/Tom Riddle/Voldemort)
Collect all of the Gold Bricks
Unlock all Animagi
Rescue all students in peril
Collect all of the house crests in Year 4
Collect all of the Red Bricks
Collect all of the house crests in Year 3
Collect 10 million studs in one level
Buy the entire Weasley family
Get True Wizard in every level
Complete the Story Levels in all four years
Complete Year Four Story Levels
Collect all of the house crests in Year 2
Defeat 20 spiders with Ron
Defeat 20 enemies with Fang
Freeze 20 characters using Glacius
Scare 20 students using a ghost character
Buy the entire Gryffindor Quidditch team from Book One
Use the Time-Turner
Collect all of the house crests in Year 1
Complete the Quidditch level within five minutes
Defeat the mountain troll, using Quirrell
Complete All Story Lessons
Complete Year Three Story Levels
Turn the sound down to 0 and music off in the options menu whilst in the library
Complete Year Two Story Levels
Knock over ten characters using a ride-able object
Complete Year One Story Levels
Collect 500 ghost studs