Super Mario Galaxy 2 Playthrough Part 20 - Final Boss

You'd think this would signal that the game is almost done, but no, this is only the halfway point (in terms of parts). In this part: Flash Black Galaxy - Jumping Around in the Dark Flash Black Galaxy - Dark Octo-Army Romp Slimy Spring Galaxy - The Deep Shell Well Bowser's Galaxy Generator - Bowser's Fortified Fortress   / compoundfraxure