This achievement is based on collecting the silver, gold and blue coins during the level to reach a set amount and as such get "true avenger". The gold bar at the top will slowly fill up as you collect the coins to help you know how you are progressing.
Interestingly, for a lot of LEGO games, you usually only fill the bar when you unlock some of the stud multipliers. However, this achievement you can actually get in the first level, without too much difficulty.
Just take the level slow, destroy everything you come across, and make sure not to die too often (as you drop coins). I managed to unlock it on the first level, when Iron Man was flying round the castle. Good luck!