Once you have all tanks and life expansions for Megaman, enter the Armored Armadillo level five times until the end. On the fifth time, when you are in the cart that jumps and leads to the Boss door, jump to the ledge to find a capsule with Doctor Light and the Hadouken Street Fighter style. Alternately, go through the Armored Armadillo level without getting hit once. At the very end, when the cart is flying through the air, dash jump to a ledge when the cart starts to descend slightly. There should be a Doctor Light capsule there, and he will give you the Hadouken attack. Note: You need full health to use this attack. Also, roll forward as if you were using it in Street Fighter 2. This move can kill anything with one blast.