l being beaten by Bowser. He later on left the meeting room to finish his other plans. When the incomplete Dark Bowser notices Fawful, Dark Bowser inhales him to finally be complete. When the final battle starts, Bowser must make his opposite lose 1,000 HP.(1,500 with Challenge Medal) The Dark Fawful Bug will not only fully heal Dark Bowser, but the bug will make him bigger, too. Bowser must punch Dark Bowser's stomach in order for Fawful to come out. Then the player must inhale Fawful for the Mario Bros. to defeat him for good.
Once the bug gets into Bowser's body, it grows to a large size. The Mario Bros must knock out his legs first. But Fawful can suck up his legs to evade attacks. It's better to destroy his glasses to hinder Fawful's sight. Then all of his body will come down because of his legs and hands being destroyed by Mario and Luigi and that leaves the most vulnerable part of his body, also known as the Dark Star Core.
After Mario and Luigi destroy Fawful, Dark Bowser will become unstable and that gives Bowser the chance to deliver the final blow to destroy Dark Bowser for good. Fawful explodes soon after.