To earn this achievement you must reach wave 5, It seems easy but it is no where easy I will include some tips to help.
Wave 1: There aren’t to many enemies but keep an eye on the overhead map and it will show you where the enemies are and line up with them and shoot them.
Wave 2: Is pretty hard there are these disc thingies and a lot of them basically for this one stay high and shoot a lot at the incoming enemies. And there will be these little glowing balls and they will be pink on your HUD.
Wace 3: This wave is nearly impossible this is when your bombs come in use and you better hope you have a lot of them. After you kill around 10-15 enemies there will be around 20 mutants chasing you around he stage and that’s when bombs come in use.
Wave 4: there are more than wave 3.
Wave 5: So many more than wave 4 and by now you have no bombs and probably no life which makes the game really hard.