Zelda II: The Adventure of Link/Rebonack

Here's an image by unwary demonstrating how to line up for and execute the easy kill on Rebonack.

Note that if he wanders right when you're on top of him, you may fall off of him and have to fight him the old, slow, dangerous way.

But if he wanders left, off the screen, and you go to the floor, have no fear. Just jump back onto him when he comes back on screen, and you can get right back to bouncing.