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