two ways I can think of
method 1 - give your bullet an instance variable set to 0. on collision with a wall add 1 to this instance variable. then when the instance variable gets to your limit (in this case 2) destroy it.this method destroys the bullet on second hit (in this case)
method 2 - give your bullet a fade behaviour set to a low fade out of something like 0.25 and not active at start. on collision with wall start fade...you could also add a particles effect for the bullet strike