Harry Potter and the Deathly Hallows - Part 1

This trophy is a very easy one, so long as you have a friend that has this game and has done the challenges. To get this trophy, ensure you have a friend that has this game, or create a duplicate PSN account and just complete one challenge on the alternate account. MAKE SURE to add that account as a friend! Go to the main menu and into challenges, then to "Online Leaderboards". Select the challlenge you know both your friend and yourself have done, and press the button to compare with friends only. Scroll up to your friend, and the trophy should pop.

To find a friend to compare with and get the trophy, use this thread:
Trophy Boosting Thread