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