Here is my idea for the final boss.
After beating chapter 10, complete a virtual training with Duo Fist V. Treble Boost. The door will not open, and the Evil Robot will trash the ceiling (again). After a short conversation, this strangely revived villain will try and defeat you... and start on the the universe!
This time, the Evil Robot uses powerful new moves:
BOOST SPREAD: The Evil Robot flies around, shooting skulls at you. :twisted:
THUNDER MAZE: Some of the tiles will glow, and will create a pillar of lightning. :twisted:
ARROW CRUSH: It rains Arrow Buster shots. Luckily the rain is scarce.
DRILL DASH: This is when you can land a hit. The Evil Robot drill into the ground and comes out of a random wall. Hit him with a full-charged Energy Blow!
After landing 20 hits, the Evil Robot spontaneously combusts - it is over, and the victory, the ultimate victory, is YOURS!