Points Awarded: 10
Achieve 100 Whammies.
Getting trickier, for this one you need to understand how Whammies work, so check out that section first if you haven't already. A good weapon combination for combos are the missiles and cannon. Rapidly alterante between the two when an enemy is in your sights and you should be able to rack up several Whammies in one go.
If you usually don't go for Whammies (and if not, why not!?), you'll need to keep this in mind an start incorporating them if you want to eventually unlock this one
If you feeling particularly cheap, you might want to switch on easy mode and repeat-rinse until the achievement unlocks...