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)
Unlock all witch characters (Single Player Only)
Visit the Hogwarts Foyer in Year 7
Unlock ALL of the Order of the Phoenix character variants (Single Player Only)
Unlock every pyjama character variant (Single Player Only)
Defeat every Harry freeplay variant as Lord Voldemort
Use a Weasley box with every Weasley
Unlock every character with a pet (Single Player Only)
Unlock every bad wizard (Single Player Only)
Unlock all of the members of Dumbledore's Army (Single Player Only)
Complete the Bonus Level
Defeat Bellatrix with Neville (Waiter) in a duel
Defeat 30 Red Caps
Collect 1 billion studs (Single Player Only)
Complete "The Flaw in the Plan"
Complete Year 8
Complete "Snape's Tears"
Unlocked on hitting 50% game completion (Single Player Only)
Complete "Fiendfyre Frenzy"
Complete "Burning Bridges"
Use a Quibbler dispenser 25 times
Complete "Back to School"
Complete the scene where Hermione and Harry dance in the tent
Complete "The Thief's Downfall"
Complete Year 7
Complete "DOBBY!"
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
Stand still with no controller input for 5 minutes
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"