0 day Attack on Earth

Beat the last mission (Paris 7) with the difficulty set to Normal. You only need to beat the last level so you can beat the game on Easy and replay the last level on Normal to pick up this achievement.

The final boss of the Paris levels is really easy. Pop off your bombs to bring its health down and then fill it with bullets when you run out of bombs. When you see the red fire shoot down its sides boost away because the fire is about to shoot out at you.