I made this thread for the people who played Super Mario Galaxy 2 and can't beat one or more of the bosses.

1. Peewee Piranha

Use the Launch Star to land on Peewee Piranha's egg and you'll crack it. And then this fight gets really straightforward. Spin near his egg and eventually you'll crack it and reveal a red thing. I will not say it, lol. Spin that and he gets angry. Now spin it once more (but he's a little faster, so yeah, but he's still extremely easy.) You done it! Nab the Power Star.

2. Giga/King Lakitu

You need Yoshi for this fight. Yay. Make Yoshi eat the Spinies Giga/King Lakitu throws and throw them back at the boss. He should be knocked out and Star Bits will be revealed. He will also use thunder attacks; just avoid this by running out of the thunder he makes. He'll eventually get angry and start punching his cloud. He throws more Spinies and his color is red, and that's how you can determine his 'angriness'. One more time you knock him and he falls. Nab the Power Star.

3. Digga-Leg
Take the Launch Star from Captain Toad's planet. Once you hit the ground you activate Digga-Leg. Grab the Spin Drills and when Digga-Leg has his glass side UNDER him, go to the other side of the planet to the opposite of where Digga-Leg is and spin-drill. Do this a few times and eventually Digga should break and the Power Star comes out of his glass side. Nab it.

4. Gobblegut
Bowser Jr. says random stuff like always before the final World 1 boss fight, and then Gobblegut appears. To defeat this dragon, hit his belly-ache bulges (the red circles) by spinning near them once he's going in the ground. They will stop for a few seconds and then they will go in the ground so hurry and spin near them. Fast. He also gets angry after some time and then...do the same thing.

5. Mandibug Stack
Extremely simple fight. Ground-pound it twice. Same with all the other Mandibug Stacks. It gets angry and faster but it's still easy.

6. Bugaboom
It's Bugaboom, a really oversized Mandibug. First phase is easy: Ground-pound it's top. The star explains everything. Then he starts flying. Nab that Cloud Flower and jump on that springboard. Make a cloud in mid-air at highest peak of springboard-jump (make sure to do a ground-pound jump on the springboard) Ground-Pound him when you can. Last phase is a little hard; he poops bombs and now he tilts when he gets near you. Do the same strategy but faster before he tilts. Nab that Power Star.

7. Rollodillo
He's a some-sort-of-turtle. He crawls around. Take one of the Rock Mushrooms and roll the rock to his rear. Now just avoid his rock shells until he gets dizzy and spin to his rear. Nab that Power Star.

8. Bowser (Not final!)
Just watch that cutscene and then...it starts. It's not final, I'm not gonna say it that dramatically now. To activate the gate, ground-pound each little planet with the pound symbol on it onto the gate onto each rock with the Bowser face on it. Now fall from the platform to the direction where the gate is and the gate should suck you in. Here starts the cutscene. Listen to Bowser's jibberjabber and the Luma sort of tells you something. Don't know. Bowser will call in some asteroids (or rocks?). Don't get caught under 'em. Then he will make a punch. Don't let him punch you, make him punch the ground. The asteroids become planets with groundpound symbols on their back. Pound them onto Bowser and you hurt him. Then it becomes straightforward. Just keep doing it until he is defeated. But remember; at the last phase, he can spit fire. Avoid that.

9. Sorbetti
Sorbetti is one of the planets that you have visited before. Land on Sorbetti's planet and that planet will fall and reveal that it's actually Sorbetti. Then Sorbetti laughs and the battle starts. Spin near his nose, that's all you do. He laughs once you get hit by him so don't get hit if you don't want to be heck embarrassed. Sort of. Just keep spinning near his nose until he is defeated and nab that Power Star.

10. Megahammer
It's a robot that Bowser Jr. made. You need Yoshi for this fight. He'll send out Bullet Bills from his nose and eventually one Banzai Bill. Eat one of the Bullet Bills and hit them at his eyes. REpeat until they're both broken completely and a Mini Launch Star should appear sending you to the back of Megahammer. Don't use it; first eat a Bullet Bill and then use it. Throw the Bullet Bill at it's blue circle on its back and repeat until it's broken completely. Once you break all his eyes and the blue circle on it's back completely, a cutscene will play and the battle continues. Now just eat the Bullet Bills and throw them at Bowser Jr.'s glass cockpit where he's sitting in.

11. Glamdozer
This is a quite disturbing fight so beware. Go under Glamdozer's Planet by gravity or the ground-pound cells which flip when you ground-pound them. (I'll call them ground pound cells.) Go under the planet and ground-pound on the cell Glamdozer is on from under the planet. He will be knocked out. Last phase he will start spitting out spheres. Avoid those. And do the same thing as you did with first phase. He should be defeated after.

12. Bowser
Same as previous Bowser fight except he makes shockwaves and the cutscene is a little different. Luma goes near his chair and then Bowser appears and Luma poops gets thrown back to the platform and is scared. But otherwise, this fight is exactly the same. Avoid the shockwaves, they hurt you as expected. His punch and the asteroids both make shockwaves so when the asteroids hit the ground, there will be multiple shockwaves so avoid those, too. And in this fight, Bowser can spit fire which actually stays for longer on the planet. Otherwise, just do the exact same thing as previous Bowser fight. Why, Nintendo.

13. Squizzard
Disturbing. Once you land on the planet, go near the sinkhole until the cutscene starts and Squizzard pops out. The battle starts. He will throw spherical projectiles to you as an attack. Grab a Fire Flower and keep avoiding his projectiles until he opens his mouth. Throw one fireball in his mouth to daze him, and throw four more fireballs to damage him once (5 fireballs needed in total with Fire Mario). He will now start throwing spikey balls. He will also throw golden spikey balls which when the ground hits, release one Coin (to gain one extra health point). Throw 5 fireballs in his mouth once it is open again (same thing as before) and then you do him another damage point. Now he will bring up cannons. They fire the SAME spikey balls that Squizzard fires, even the golden ones. The cannons can be defeated with the Fire Flower but they will regenerate after some time. He will also throw 2 large bombs at Mario. Do the same exact thing (throw 5 fireballs in his mouth once open) and Squizzard is done for. Grab that Power Star (don't be scared by how high it is in the air).

14: Prince Pikante
It's a green Octopus (that's the name of the enemy...!) riding in a tank. He will spawn projectiles, one from his mouth and three from his cannon (so lazy ;-. The rocks will create small lava puddles. Don't touch them or Mario/Luigi get their butts burned. Skate around the icy arena. (But you may have a hard time avoiding the puddles and rocks since traction is terrible on ice) He will eventually throw a coconut. Throw the coconut back to Pikante and you have him one damage point. He will move slightly faster. Repeat the same coconut strategy. He will turn red and move faster, and be able to throw 9 rocks. He gains a new attack; he can now face upwards and throw rocks and coconuts upwards. The projectiles will fall back down slowly. Just do the same coconut strategy and he is done for.

15: Boomsday Machine
Bowser Jr. made yet another machine! It's a tower-like boss. Bowser Jr.'s relaxing in a cockpit and you need to break it. No idea why the cockpit controls the entire machine. Just grab a Cloud Flower, go to the wind blowers blowing wind upwards and make a cloud and then the cloud will get pushed up by the wind. Now keep making more clouds until you reach Bowser Jr.'s glass cockpit and ground-pound it. You deal one damage point to the boss! The second phase is like the first except that the Boomsday Machine will now attempt to vacuum the place, sucking the clouds since it's vacuuming. There's also an electric shield covering Bowser Jr.'s glass cockpit. Use a cloud platform to wait this out until the shield is off and ground-pound the glass cockpit again. The third and final phase has the Boomsday Machine going mobile. It can now move. Just do the same thing as before. You still need to watch out for the vacuum, the firebars and yellow projectiles. Do the same thing as first two phases. You have defeated the Boomsday Machine, congratulations. Onto a veryyyy familiar fight. You're gonna enjoy the one after this.

16. Whomp King
Wee, it's Whomp King from Super Mario 64. Enter the hole to start the fight. He says some familiar dialogue and then the battle starts. The strategy is similar to Super Mario 64's Whomp King. He smacks the ground with his face and you need to ground pound its back. He will get up. When he tries crushing you he also stuns you (you have to jump at the right time to not get stunned). Whomp King can stomp his foot to spawn Whimps which try to aid Whomp King in battle. Don't forget, when Whomp King actually does manage to crush Mario or Luigi, he INSTANTLY lose a life no matter how many health points he has. Also, that ground pound glitch from Super Mario 64 no longer exists.

17. Fiery Gobblegut
Same fight as Gobblegut except he's...now...fiery. Free lava puddles are made for you. And you burn and run around and you can't spin if he hits you even once. After some damage points he starts spitting fireballs which make lava pools where they hit. Otherwise it's all the same. 10 Star Bits are released by one bellyache bulge you hit. Remove all of them to defeat Fiery Gobblegut.

18. Bowser (final yay)
First phase is the exact same fight as the previous two! But he can now create shockwaves like lines all over the planet by his punch. But it retains the other same strategies. And I think the fire stays for much longer. Also sometimes the planets are knocked off by Bowser. Watch out for that. And then once you defeat his first phase, the last phase comes. It's much different, thankfully. But it may seem that he has been defeated right in the first phase; just go and try grabbing that Grand Star. You have to, actually. And then Bowser appears. Again. But it's different, so not to worry. Bowser eats the Grand Star to make himself much bigger. It's a giant turtle!! He now starts the final phase. You're on asteroids (literally) and you need to pound them to Bowser, who's in the air. There's no planet; just the small ground pound ones. Bowser will get closer and closer to you by spinning; keep pounding the asteroids to Bowser and don't let him near you. Knock him over and over till' he's gone. YOU BEAT THE GAME. But it's not the end of bosses, no!

19. Dino Piranha (Not Peewee, I mean Dino)
Use Launch Star to crack his egg once and then spin near his egg to let him out of the egg. Now just spin near his tail over and over and it'll keep smacking his head. After sometime, you defeated him! Easy as cream pie. I guess.

20. King Kaliente
Planet after Dino Piranha has King Kaliente, both from Super Mario Galaxy 1, like all bosses in Boss Blitz Galaxy! He spits fiery rocks and some coconuts. Knock the coconuts back at King Kaliente to deal him damage points. Next phase he spawns Blue Podoboos and he can now knock back the coconuts; play a little ball game by knocking the coconuts back when he sends them to you. The coconuts will eventually hit him and he'll be defeated.

21. Major Burrows
Just spin near him when he gets out of the ground in search for the nonexistent Star Bunny. The battle starts. He drills in the ground. Watch out for that trail he leaves in the ground which you can see faintly. When he shows his spikey shell, that means he's about to come out. When he comes out a bit, ground pound near him (near him, not on him) to get him out of the ground; he'll try running from you. Spin near him and you have him one damage point! Second phase has him much faster and you need to ground-pound near him two times. Do same thing, other than that. You defeated the mole!

22. Bouldergeist
Okay, he spawns rocks. Black ones spawn Bomb Boos, gold ones spawn Coins and gray ones spawn nothing. Take the Bomb Boo(s) and throw them/it at Bouldergeist. Repeat one more time at his ghostly form. Second phase has him growing...HANDS. He can now punch you and do a cooler animation when he's summoning rocks. Awesome abilities I guess! And just repeat until he's dead. Pretty dang straightforward, in my opinion.

23. Fiery Dino Piranha!
You get a refresher planet. Just take the Launch Star. The fight's the same as Dino Piranha you just fought a little time ago except it's now fiery! Make sure you do not hit his tail while he's on fire; that'll hurt you instead. When he temporarily gets unset from fire, hit him right at that moment. Second phase has him faster like before AND he now spawns fiery projectiles. Just repeat the previous strategy again and...

YOU DEFEATED ALL SUPER MARIO GALAXY 2 BOSSES! Enjoy, hope this guide helped you, took me a long time so uh yeah