Here is the full list of all 49 LEGO Harry Potter: Years 5-7 achievements worth 1,000 gamerscore.
Use a Weasley box with every Weasley
Defeat Bellatrix with Neville (Waiter) in a duel
Complete the game to 100% (Single Player Only)
Complete the Bonus Level
Unlock every character with a pet (Single Player Only)
Unlock every pyjama character variant (Single Player Only)
Unlock all of the members of Dumbledore's Army (Single Player Only)
Unlock every bad wizard (Single Player Only)
Unlock ALL of the Order of the Phoenix character variants (Single Player Only)
Unlock all witch characters (Single Player Only)
Defeat every Harry freeplay variant as Lord Voldemort
Collect 1 billion studs (Single Player Only)
Defeat 30 Red Caps
Unlocked on hitting 50% game completion (Single Player Only)
Stand still with no controller input for 5 minutes
Use a Quibbler dispenser 25 times
Complete Year 8
Complete "The Flaw in the Plan"
Complete "Snape's Tears"
Complete "Fiendfyre Frenzy"
Complete "Burning Bridges"
Complete "Back to School"
Complete "The Thief's Downfall"
Complete Year 7
Complete "DOBBY!"
Visit the Hogwarts Foyer in Year 7
Complete the scene where Hermione and Harry dance in the tent
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 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 Year 5
Complete "A Veiled Threat"
Defeat Bellatrix as any Sirius Black character variant in a duel
Complete "A Giant Virtuoso"
Complete "Kreacher Discomforts"
Complete "Focus!"
Complete "Dumbledore's Army"
Complete "Dark Times"