Here is the full list of all 41 Harry Potter & The Order Of The Phoenix achievements worth 1,000 gamerscore.
Completed discovery level 13.
Beat all Gobstones champions.
Found Luna's lost belongings.
Found Fred and George's hidden parcels.
Finished the story on the hardest difficulty.
Finished the story.
Met all the characters in the game.
Unhinged Umbridge.
Got an 'O' in all lessons.
Discovered all known areas of Hogwarts.
Completed all the teacher mini-quests.
Beat all Exploding Snap champions.
Tidied up Hogwarts.
Completed discovery level 12.
Uncovered all the hidden Hogwarts symbols.
Completed discovery level 11.
Found the hidden wizard plaques around Hogwarts.
Found all the house ghosts of Hogwarts.
Challenge Cup unlocked: Found all the secret wizard chess statues.
Discovered the password for every shortcut portrait in Hogwarts.
Completed discovery level 10.
Cast 500 successful spells.
Beat all wizard chess champions.
Completed discovery level 9.
Completed discovery level 8.
Completed discovery level 7.
Completed discovery level 6.
Found all the flying creatures of Hogwarts.
Found all the rare creature tracks hidden in Hogwarts.
Completed discovery level 5.
Completed discovery level 4.
Completed discovery level 3.
Cast all defensive spells in a single encounter.
Recruited Dumbledore's Army.
Covered 9 3/4 miles.
Completed discovery level 2.
Recruited 20 members of the DA.
Recruited 10 members of the DA.
Discovered the Room of Requirement.
Completed discovery level 1.
Arrived at Hogwarts.