LEGO Marvel Super Heroes 2 100% Guide
To unlock this achievement you must first achieve 100% within the game and then enter the room at the back, inside the Avengers mansion with a trophy symbol next to the door. Once inside you will see a fountain, pull the switch to release the LEGO studs and balloons, the achievement should now pop.
This is possibly the biggest and most complex LEGO game to date and to achieve 100% you must achieve the following criteria:
Complete all 20 story missions and get "True Believer" status by collecting a set number of LEGO studs per level.
Complete all 10 Gwenpool side missions and get "True Believer" status by collecting a set number of LEGO studs per level.
Find and Unlock all 10 Pink Bricks hidden within the Gwenpool side missions. (Note: there are 17 Pink Bricks in the game, you start with 7 available to purchase. I am not sure if you need to purchase these to achieve 100% but i highly suggest you do anyway as the stud multipliers are almost essential for buying everything in the game.)
Collect all 200 minikits hidden in the story missions. 10 minikits per level.
Save all 50 Stan Lee in Peril's. 20 in the story missions, 10 in the Gwenpool side missions and the remaining 20 are hidden around Chronopolis.
Unlock and purchase all 236 Characters and Vehicles. Characters can be unlocked in a variety of ways including completing story and Gwenpool side missions, each of these missions also have a single hidden character card to find, completing side quests and races around Chronopolis and playing a match in Battle Arena to unlock Grandmaster. Vehicles are unlocked by completing free roam challenges around Chronopolis.
Complete all 25 free roam Challenges around Chronopolis.
Complete all side missions dotted around Chronopolis.
Complete all Races dotted around Chronopolis.
Activate all 14 Gold Brick statues around Chronopolis.
Collect all 255 Gold Bricks. You also collect these Bricks from completing the majority of the list above and by completing the Gold Brick puzzles around Chronopolis.
Once you have met all these requirements you will be the proud owner of the Nuff Said Achievement and 200 gamerscore.
Hope this helps and Enjoy!!
UPDATE: It would appear that when you purchase any of the DLC levels your stats get updated in-game meaning you will also need to 100% them to unlock this and other collectible related achievements.