Earth Defense Force: Insect Armageddon

I got it when I was working on "Good Start". You just have to destroy 1000 small gunships shooting at you. A good level for this is playing in survival mode 4 Original Sin, where you can work on other achievements such as "Good Start" (I recommend playing in coop mode) and "Survive-o-Rama" (although in this case there is probably an easier method)