i got this trophy using the tutorial level using the tank,when you are told to melee the first enemy avoid using melee and keep shooting it but try to be careful and shoot slowly as possible(you will have two shots each time you use the energy gun),ensure that you have shot more than 300 bullets,after that you need to kill 3 or 4 enemies by shooting them(be careful not to harm the accuracy)then you kill the last enemy using a grenade,once you take the chopper the trophy will pop a few seconds after