Here is the full list of all 49 LEGO Harry Potter: Years 5-7 achievements worth 1,000 gamerscore.
Defeat 30 Red Caps
Unlock all of the members of Dumbledore's Army (Single Player Only)
Unlock every character with a pet (Single Player Only)
Unlock ALL of the Order of the Phoenix character variants (Single Player Only)
Unlock all witch characters (Single Player Only)
Defeat Bellatrix with Neville (Waiter) in a duel
Collect 1 billion studs (Single Player Only)
Unlock every bad wizard (Single Player Only)
Unlock every pyjama character variant (Single Player Only)
Unlocked on hitting 50% game completion (Single Player Only)
Visit the Hogwarts Foyer in Year 7
Complete the scene where Hermione and Harry dance in the tent
Complete Year 8
Complete "The Flaw in the Plan"
Complete "Snape's Tears"
Complete "Fiendfyre Frenzy"
Complete "Burning Bridges"
Complete "Back to School"
Stand still with no controller input for 5 minutes
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
Complete Year 6
Complete "Horcrux and the Hand"
Complete "Felix Felicis"
Complete "Love Hurts"
Use a Quibbler dispenser 25 times
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"
Complete the Bonus Level
Complete the game to 100% (Single Player Only)
Use a Weasley box with every Weasley
Defeat every Harry freeplay variant as Lord Voldemort