Whispy Woods
Difficulty: Very Easy
Description: A large tree with hollow eyes and a pointy nose.
World: Vegetable Valley
HP: Six Hits
Since Whispy Woods cannot move, its attacks are very limited. This makes it pretty much the easiest boss of the whole game, and defeating it without losing health is plausible, even if you have no ability. Whispy Woods has only three different attacks. These inclue dropping a few apples on you, puff out two clouds, puff out four clouds.
First comes his apple attack. Three small red apples fall out of his branches above, rolling around on the ground to hit you. These are very easy to avoid, as once all of them have fallen you can just float around above them. However, when you have no copy ability, these are the way to attack Whispy Woods. Simply swallow one of the apples, then spit it back out towards Whispy Woods. It will cause him a fairly large amount of damage.
The second two attacks involve him puffing out clouds, which are sent forward in attempt to hit you. These, also, are easy to avoid. Either jump over them or alternatively get closer to Whispy Woods and let them pass right over you.
The simplest strategy is, of course, countering Whispy Wood's apple attack by spitting them at him. It's possible to counter all three apples right away, killing him very very quickly. The other way is by just using your ability, whatever it may be. Just stand next to him and go all out! Other then watching out for apples, nothing should hurt you.
 Paint Roller
Description: A round orange circle on roller skates who holds a paintbrush as his weapon.
World: Ice Cream Valley
HP: Six Hits
Unlike Whispy Woods, Paint Roller has a much larger arsenal of attacks. His roller skates and high jumps allow him to move quickly throughout the area. Having said this, he is not too hard to defeat. Now, Paint Roller never tries to physically touch you, but uses his four easels to draw enemies that will try to hurt you. He can draw all of the following creatures: Waddle Dee, Kirby, Umbrella, Baseball, Cloud, Microphone, Car, and Bomb. The enemies in bold are the ones that you can swallow to gain an ability!
Pretty much the only way to kill Paint Roller is by gaining one of the powers that his minions (paintings) possess. All of the abilities will hurt Paint Roller in some way if you use them correctly, but the one that seems to work the most effectively is the Spark power, which you gain by swallowing a Cloud. When you obtain this power, stand fairly close to Paint Roller and let the sparks fly! Paint Roller is too busy drawing to quickly get out of the way, so the electricity quickly zaps the life right out of him. Of course you can always just inhale one of your enemies and spit it back at him too.
The thing that makes this boss fall into the medium category is how to avoid him while you're waiting to gain an ability. His movements across the stage are random and unpredictable, and like I said earlier he is not on the slow side. Just stay aware of him at all times, and floating around in the very middle of the stage might not be your brightest choice. One of the safest places to hang around may be directly above one of his easels. He'll only skate right below you, if he does at all. But once he chooses his next painting site, hurry up and get in position for your next attack.
 Mr. Bright & Mr. Shine
Description: A sun and a moon that take turns attacking you. Also known as Mr. Sun and Mr. Moon.
World: Butter Building
HP: Three Hits Each
Now, in this boss stage, Mr. Bright and Mr. Shine will take turns fighting you while the other floats in the sky, attempting to slightly hit you in some more subtle way. First we'll talk about what each of them does while they're on the ground. Mr. Bright has three main ones: Giant Leap, Roll, and Fireball. In Giant Leap, he takes a big jump and tries to land on top of you. There's no way to truly predict this, but you should have time to scurry away while he's in the air. When Mr. Bright is about to throw a Fireball, he'll quickly clap his hands together giving you time to react. When he's about to roll, he'll flash and jump backwards. In that case just float above him and he'll pass right under you. Mr. Shine's attacks are pretty similar. He either does his Giant Leap, which is identical to Mr. Bright's leap, Roll (also like Mr. Bright's), and Cutter. Cutter is by far his most dangerous move, as it's easy to miss the signal: putting his hand back. Both Mr. Bright and Mr. Shine will also perform small jumps just trying to hit you. If you just float above them this is easy to avoid. After about five turns, the boss on the ground while float back up to the sky and the other one will come down.
Now, let's talk about Mr. Shine while he's in the air. While up in the sky he is invincible, so don't focus on hitting him. He will flash, then eight stars will drop from the sky. If you swallow the star you will gain the Cutting Power, but spitting the stars right back at Mr. Bright (who's will be on the ground) is probably easier. Mr. Bright in the air is slightly different. He will flash, then float directly above you and shoot a small wall of fire down. On each side of the beam will be a star, which can give you the Fire Ability. It's a good idea to spit one of them at Mr. Shine, and swallow the other one to become Fire Kirby.
Most of the best strategies were already described in the Attacks section. Just inhale the stars that are created from an attack and spit them right back out at the boss who is on the ground. Once you hit one of them three times, that boss will resort to the sky and no longer attack you.
Difficulty: Medium, then Very Easy
Description: A large cloud with one eye.
World: Grape Garden
HP: Six Hits
There are two different parts of the battle with Kracko, the first being the hardest by far. First of all, make sure you gain the Hi-Jump power by eating the enemy on the stage. Then, Kracko will appear spinning around the floor, destroying everything he touches. Use the Hi-Jump ability to jump quickly to the next cloud before it's too late. If you mess up and miss, you will fall down and lose a life. You have to jump 17 times before reaching the second stage of the fight.
When you reach the stage, wait for Kracko to turn into a regular cloud. Now, he has four new attacks. The first one is Lightning Bolt, where he will move closer to the ground and slide across the stage. The second is Swoop, where he'll fly across the stage, touching the middle of the ground. Next comes Move, where all he'll do is move from one side to the other. And finally Spit, where he'll release an enemy with the Hi-Jump power.
Kracko always uses the same first two moves: Lightning Bolt, then Swoop. The way to kill him is just gain the Hi-Jump Ability and keep ramming in to him. Just be aware of what moves he's using so you can stay out of trouble while you're preparing for the next jump. Six hits and he's dead.
 Heavy Mole
Description: One eyed digging machine.
World: Yogurt Yard
HP: Six Hits
The Mole actually has a pretty small amount of attacks. The stage in which you fight him is created by the Mole himself, and is a dirt tunnel. The first attack is with his blade. It will be released and spin around a random pattern, then settle back on to the Mole. The other attack is spitting a Bullet out. Now, this bullet has the potential to have two different abilities when swallowed. About 3/4 of the time it is a Hammer Ability. But, the other 1/4 of the time it turns you into Sleeping Kirby! This is bad if you are too close to the edge and fall off while Kirby's getting some Beauty Sleep. So, if you decide to Swallow the bullet try to get to safe ground first.
The easiest way to beat Heavy Mole is with the Hammer ability. Just jump close to him, press B to do a hammer spin, then slowly back away and wait for the next opportunity. Six hits and bye bye Mole!
 Meta Knight
Description: Similar appearance to Kirby, but with a cape, sword, and mask.
World: Orange Ocean
HP: Ten Hits
Meta Knight is easily the hardest boss in this game, and you're given a sword to fight him. He has many attacks that won't be all listed. The attacks that center in the air are the ones you should watch out for. Since it's almost impossible to avoid them all while on the ground, you should definitely float around over half of the time. But when he does jump up, quickly float down, and hit him as he is landing. Then get right back up in the air.
The best strategy is the one where you hit him as he's landing. You can always try predicting the many moves he'll pull off, but you're risking the chance of being hit. If he does manage to hurt you, quickly slash him around three times when you're invincible from the recent hit.
 King Dedede
Difficulty: Medium Hard
Description: Greedy King with a giant hammer.
World: Rainbow Resort
HP: Ten Hits
King Dedede has six different moves. The first and most simple is where he walks towards you and then tries to body slam you with a short dive. He normally starts the battle with this attack, so you can just float above him. Another attack is where he walks towards you again, but this time jumps up and bangs his hammer down. This attack creates a star, which you can inhale and quickly spit back at him. King Dedede may also just try to hit you with the hammer without jumping, this also creates a star. Another one of King Dedede's attacks is trying to Inhale you, then spit you back out. Then comes where he puffs up and floats around the screen, trying to hit you. And finally comes his super jump, where he bounds across the screen and tries to land on you, creating two stars. The stars that he makes do not give you an ability if swallowed, but if you don't have an ability already they are the only way to defeat him.
The first strategy is using the stars that are provided by several of the King's attacks. Just wait until you are at a safe distance from him, shoot it quickly while he's walking towards you, then float away before he can attack. Next comes from using the Hammer Ability, this is one of the easier methods. Just hit him with the hammer at the following times: In his back when he's trying to inhale you, when he's completed a dive, when he's floating around, or in the back when he's completed banging his hammer down. The third way is using the Laser ability to just keep your distance and shoot whenever he's in range. And of course several other powers that Kirby can have will most likely help in some way.
 Nightmare (Part One)
Difficulty: Medium Hard
Description: An evil looking bubble that shoots stars at you.
World: End of Game
HP: Fifty Hits
The first part of fighting Nightmare has several different attacks: Shoot three stars in a row, shoot three stars at the same time that create a fan formation, shoot two stars at the same time that create a small tunnel, shoot beams, swoop in a circle, or ram you. Create four stars that shoot at you straight or diagonally.
Now, in this battle you are given a star rod as your only weapon, so all you can do to hurt him is shoot rapidly. But, to save all the life you have, don't go at it with a completely random pattern. Take time to understand his attacks. But, be very careful. The thing that makes this boss hard is: You only have 65 seconds! If you aren't fast enough Nightmare will disappear and the floor will crush you. So, stay on the left side of the screen shooting rapidly, and move up and down to avoid his attacks. One of the hardest is the four stars that he shoots at you. But if you stay in the left middle of the screen, none should ever hit you!
 Nightmare (Part Two)
Difficulty: Medium Easy
Description: Scary flying tornado.
World: End of Game
HP: Six Hits
Surprisingly, this Nightmare is pretty easy to beat if you have at least three HP left. There is one very easy trick to dodging his many attacks: duck in the bottom left-hand corner. Pretty much nothing will ever hit you! Just come out for a brief second when he reveals his tornado and hit him with a star. Only six times and Nightmare is defeated once and for all. YOU WIN!