Defeating Emperor Bulblax
Take about ten Purple Pikmin and use the Ultra-Spicy Spray on them. Throw them all on the giant Bulblax. The Boss should be defeated in just a few seconds.
You must be willing to sacrifice a few Yellow Pikmin for this trick. In the Final Trial area, once you are ready and have cleared a path leading to the Emperor Bulblax, get about 10 to 15 Yellow Pikmin. Then, head up the path straight to the round-shaped arena. Sneak past the Emperor Bulblax and you will see a hill leading to the top of the arena. Go left and right, searching for as many bomb-rocks as possible. Then, go back to the bottom of the arena and wake up the Emperor Bulblax with Captain Olimar. Once he has awakened, get directly in front of him. He will open his mouth with his huge tongue and will slurp them up. After that, right inside his stomach, a huge explosion will happen inside his body and a huge chunk of his health will be wiped out. Repeat this until you are out of Pikmin, and he will probably be dead by then. Note: On your way up the hill in the arena, there will be a gate.
This Boss is found in the Cavern of Chaos, Bulblax Kingdom, Hole of Heroes (x2), and Dream Den. Defeat it by throwing Pikmin at its face. Do not attack it head on, as it will eat a lot of Pikmin. Call the Pikmin back when it flinches. It may stomp on you. In the Cavern of Chaos, make it lick bomb rocks by luring it by them. In the Hole of Heroes, defeat the one that swallowed the treasure. One will be guarding the hole to the next floor. Avoid it by making the president take all the Pikmin, and put him in a safe location. Then, use Olimar to go to the floor's hole, and you will be unharmed.
At the Cavern Of Chaos, dismiss your Pikmin when you see the Emperor Bulblax. Wake Emperor Bulblax and put him near the bombs. He should lick them then he should gobble them up. He will then lose a chunk of HP.
Use the following trick to defeat Emperor Bulblax in "Hole Of Heroes" without losing Pikmin. In a sublevel in the Hole Of Heroes with a lot of Emperor Bulblax and bombs laying everywhere, place your Pikmin in a safe spot. Venture off to wake up all of the Bulblax without touching the bombs. Stand next to a bomb or two and let the Emperor eat them. This will take out a large amount of his HP. Do with all Emperors and you will not lose any Pikmin.