I just got done doing it with Fox. Knowing what to dodge, and when, is the key. I beat Duon without taking damage, and it was funny how I did it too. He launched his missles, and I jumped into him, and put up my sheild. Of course, the shield broke, but becaue of my position, ALL the missles hit Duon, and he died from it.
Meta Ridely: Wait for that rapid spit attack he does, get infront of his mouth, and put up the reflecter. If done right, you can Pretty much knock him out in just that one attack. You can also reflect his gigantic balls of fire.
Pete: I dont need to say anything. Anyone should be able to beat this guy with 0 damage.
Raquaza: He gave me the hardest time, I always got hit when he would fly straight up and come at me from the side. I always wanted to roll dodge, thinking he would come back down, and get hit from the side. You can reflect his electric ball back at him for some decent damage. Basically, spam a smash or two, jump away, dodge attack, rinse, repeat.
Ridely: He's easy, readable, not to much trouble.
Porky: Lazers Lazers and more Lazer. Get away from the guy and spam it. When he drops those walking bombs, run right past them all and they will all explode, missing you. Air dodge the tacking lazer, and for the floating lazer, just outrun it.If he's slowing walking towards you (and not that step attack) He's setting you up for a rapid stab. Dont let him near you.
Golem(Dunno his real name): First off, get close to him right away, as he's gonna toss missles. They'll miss and hit the ground harmlessly. They just Zip around him with Fox illusion to make him miss his moves. If he's facing off the screen, he's gonna attack that way, of course. He's pretty readable too.
Hands: Again, I shouldnt have to say anything.
Tabuu: This is just a case of knowing the bosses attack patterns. He's not that hard if you can dodge his attacks. The RRoD are deadly, but just practice in SSE if you really have trouble dodging. Watch the video of the fox player up above and learn his attack patterns. there IS one other attack he does that wasnt shown there, that I've never seen him do before. He causes a string of sparkled dust to appear straight out, and an explosion happens in all of those spots. I didnt even know he could do this attack, and I dodged it. You shouldnt have a problem. When he gets big and shoots lazers, this attack is the EASIEST to avoid out of ALL of his attacks. Wait till he starts with the lazers, jump up, and Spam down B to Hover. When you have about a splitt second, (And you'll get a chance, its small, but its there) drop down, and jump back up and Hover again between the attack, if you dont, he will most likely hit you with that lazer on the way back down. The rest of his attacks are just a case of knowing what to do when. Mostly, jumping.
Duon: LAZAH. Spam it. Its your friend. Right off the bat, spam it. He's gonna roll at you, or roll up and try and slice at you (which is easiely dodge by a roll dodge). You can reflect the Pink sides bullets it'll shoot at you, but you CANNOT reflect the lazer, just try and dodge it. The Blue side isnt that deadly. Your Biggest chance comes when he fires the missles, get close, (on the other side of him if you can) and try and get the missles to nail him, it causes a MASSIVE amount of damage on him.
I hope this helps whoever is having trouble. REally, do what that Fox in the video does, and you'll have no problem.