Just Barely!~
Cleared any stage with 0.5 lives and 0 bombs. Xbox 360 / Arcade
At the top left of your screen are 3 bars which are your lives. when you get hit with a bullet your health can either deplete a full bar or half a bar. pretty much the easiest way to get this is to play on difficulty 1 and on whatever first level you pick. save your bombs till the boss fight. first get the bosses health down to half way [give or take]. then depending on your health, purposely run into his bullets until you get down to your last bar and its only half full. (A bullet takes off a full bar; running into an enemy removes half a bar. If you need to drop the last half a bar, wait for the boss to take a break from firing and quickly ram into them.). once your health is on last half (0.5) start spamming your bombs. even though your invincible when you use a bomb still be careful to dodge any incoming bullets. make sure you use all your bombs. if the boss still has a little life left finish him off with a regular attack. the achievement should pop up sometime after the bosses death scene.