Penance Grub-dog

The Penance Grub-dog the most powerful member of the Grub-dog family. It is made up of all of the creatures in the Grub-dog family. Yes, all 31 of them. It looks like a mish-mash of many different Grub-dog parts attached to Pikmin 1's Emperor Bulblax, creating a truly horrible-looking creature.

How-to-Kill
The best option would be to run away as fast as you can, but if you really want to here is how to kill it.

Pikmin
When the creature rears up to do a Sonic boom swarm your Pikmin around its twelve(!?) feet. Because of its huge top-heaviness, it will fall over, leaving its soft underbelly exposed. Then chuck Pikmin at it like you never have before. If you have chucked fast enough it should get down to ¾ health. Repeat until the desired effect is achieved (Killing it, for those who didn't know). It will drop a piece of paper for you to take back. The paper's only purpose is to show off to other players that you defeated this horrible monster.

Captains
Trying to kill it with your captains is both insanely stupid and impossible. To put it in perspective, most of its attacks will kill your captain in one hit.