Round One:
David Bowie looks at his watch and realizes that the apocalypse was supposed to come about almost ten years ago. Hoping that the fiendish masters he serves don't get too upset for his tardiness, he begins plotting the demise of all creation. In order to bring about the end times, he will need the Right Hand of Doom, which is currently serving as Hellboy's right forearm. As such, like several other villains before him, he seeks out Hellboy with the intent of taking control of the Right Hand of Doom and destroying the universe.

Rather than send out incompetent minions to accomplish this task, Bowie decides that he'll need to do it himself. He confronts Hellboy in person and determines that the big red brute is too much of a challenge to take down in a prolonged fight. So he decides to end matters quickly -- by cutting off Hellboy's right arm with a katana. David Bowie moves fast, and before Hellboy is even fully aware of what's going on, his arm is cut off at the shoulder and flopping around in front of him. Round One goes to David Bowie.

Round Two:
Missing his arm hurts, but that doesn't mean that Hellboy will go down. He is a hellspawn with physical strength and stamina that is off the charts, and he keeps fighting. His other arm might not be indestructible, but it does have super strength. He decks David Bowie as hard as he can, sending the rockstar flying about twenty feet back. This buys him enough time to pick up the arm and hold it to the stump on his shoulder. His incredible healing factor combined with the magical powers of the arm help to reattach the limb in a matter of moments. (No, I don't know if this is possible given Hellboy lore - sue me.) Back to full health, Hellboy re-enters battle, pressing the attack against David Bowie now that the element of surprise has been eliminated. Round Two goes to Hellboy.