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