While in Dumbledore's Office, go to his desk to select challenge mode. Play all of the extreme challenges and beat them for this achievement. It is best to complete the story before attempting these because they are all redoes to minigames during the story. Just keep trying at these, the two that were the most annoying for me was the Greenhouse one and the Minecart track one. For the greenhouse one just try to move the agitated plants to the closest empty pot not the ones open at the far end right away. Also there will be two slug attacks back to back, so don't put away your repellent until you get those two. For the Minecart track one, try to memorize the track, only lift your cart just slightly when going over broken track. And try to get past the first part without having over a second of lift time or so. Just keep trying at both of these and you should get them with a little practice.