Mega Man X Hadoken

Stage: Armored Armadillo

Necessary items: All Heart Tanks, Sub Tanks, Upgrade Capsules and boss weapons.

You can access it in Armored Armadillo's stage after collecting all 4 armor upgrades, all 8 Heart Tanks, and all 4 Sub Tanks (note that you don't have to fill the Sub Tanks).

Near the end of the stage, you'll come across the final platform that you can ride through the mine. Ride the platform until it flies off the track and out of the mine; dash jump off and climb the wall!

Note that you need to visit the top of this cliff FOUR times (Just SEEING the top of the cliff counts as a visit, so as soon as you see the energy pack you can exit/die/finish the stage safely and it will count as a visit) BEFORE the Hadoken capsule appears (so it will appear on your FIFTH visit). These visits do NOT need to be subsequent, which means you can visit once while completing the stage normally, and then just visit three more times once you've collected everything later in the game and the capsule will appear.

You can perform this move by doing DOWN to RIGHT TILT + Y, note that your life needs to be FULL in order to perform the Hadoken, otherwise it will not work.