Super Dracula or Fangs is the boss of Monster Island.
At first, the Dracula boss may seem quite tough. It moves rather freely around the screen, albeit slowly. When he stops, he releases a large number of bats that radiate outward from him in an arc. The truth is, however, that all of the bats are susceptible to your rainbows, so if you arrived with fast triple rainbows, you can take all of them out in one fell swoop. In fact, with that kind of power, it's easy enough to lay a bunch of rainbows out and wait for Dracula to stop right in the middle of them before jumping on them and crushing Dracula with all of the rainbows you created. With that strategy, you should be able to take him out pretty quickly. If you didn't arrive with triple rainbows, you'll have a tougher job ahead of you, but it's still possible as long as you stay out of his way while he's moving around the screen.