Skate 2: Cooperation is Key 10 GS

To get this you'll need to complete 50 online freeskate activities with your created skater. This can be obtained really quickly if you play for a bit.

Hard, start a career and create your skater. After finishing the tutorial you should be able to safely exit to the main menu, from here select "freeskate" and choose your created skater. Wait for somebody to propose an activity or do so yourself by pressing back, then selecting "Freeskate Challenge". Do this 50 times in order for the achievement to unlock.

Hope you unlock this achievement and have fun!