The easiest way to get the achievement is the first stage in EASY mode.
Start the game normally in EASY mode, then follow up to the part where the tank.
See the picture below.

Once you get the tank do not spend the cannon fire, now just go to the BOSS.
Once you get it, shoot 8-10 cannon fire in the boss, stay as close as possible to the BOSS, then press in the same time, the fire button and the jump button (If you are using Xbox 360 or Xbox One control, just press A + B).

See the video below how it should be done.