The Hadoken

The Hadoken is the secret upgrade only collectable under specific circumstances. It deals 32 damage to enemies, which happens to be the size of a boss's life meter.

Requirements to Collect

You must have 100% other than the Hadoken:

• All 8 heart tanks, one in each stage
• All 4 sub tanks, from Eagle, Mammoth, Armadillo, and Mandrill
• All 4 armor pieces, from Penguin (Boots), Chameleon (Chest-plate), Eagle (Helmet), and the Buster from either Mammoth or Zero (the run collects it before going to Sigma Stages, so this requires Mammoth

You must also see a specific pixel on the screen at the end of Armadillo's stage 4 times, and the capsule will appear& on the 5th "visit". This is the right edge of the screen behind the life drop above Armadillo's boss door.

Although it is not required to take deaths here, most runners do. Jumping into the pit to restart at the midpoint of the stage is faster than exiting the stage through other means.

The number of visits requires collecting a 1up on an otherwise deathless run if you use the jump into the pit method. The route usually collects the 1up in the open of the second half of Chameleon's stage.

The other classic technique for farming extra lives is to use charged Armadillo at the start of the stage, and continuously kill and respawn the "classic mega" ball bat. It is known to have a high 1up drop rate.

You must also have full health when you arrive for the final visit to collect the hadoken. You do not need full subtanks.

The hadoken is typically not retained across using a password, but there is a way to keep it.

The hadoken is performed as it is in Street Fighter, by rolling the thumb from down, down-forward, forward, then shoot. You must have full HP and the buster equipped. The timing takes some getting used to, as the Mega Man hadoken requires pressing Y after forward. 

The detection of diagonals is slightly off, so you may be able to press down-down-forward to achieve a hadoken.