I still haven't got to Tabuu on Intense. I thought I was there a while ago, but that mech that transforms into a tank pretty much destroyed me. It's frustrating when you have like 30-40% damage and they do an attack that sends you flying, but I'm making progress. 

I tried Fox like appolose said and he works great against Ridley when you fight him on the ship. I'm having more problems against that dragon thing with Fox than I was with Toon Link. And of course Porky is a pain now. That tank mech is giving me hell. I've had some success with Fox, but just haven't got there yet.

Lucas is working well on some bosses, others not so much. What I really like about him is that you can use his down+B against certain attacks from Master Hand and Duon to heal damage. I'm having problems with the same bosses with Lucas as I am with Fox though. 

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I would work on trying it with Toon Link, you'll get to Tabuu eventually and if you know how to dodge his red rings of death you should have no problem beating him. (I still need to pratice that though).

I find trying to get behind Raquaiza's (the dragon) head when pogoing on him reduced the chance of falling off or being hit with his spark attacks.

Duon (double mech) I find pogoing onto the head facing away from you saves you the risk of being hit alot and if he starts to spin just do your upper spin attack to get away from him or at the very least reduce the amount of damage you're taking.

Goleam (transforming tank mech) is still unpredictable but more times than not you should do well against him.

Porky, just try and stay on top of at all times, even when he charges his golden spark beam, just move to the side of it to only take a little damage or none at all as the beam will most likely miss you all together. When he jumps up into the air with you still on top to do his red seeking shock attack on targets below, just jump up and start pogoing again so you won't be shocked when he starts firing.

For more boss battle hints... http://www.smashbros.com/en_us/gamemode/modea/modea15.html

I'm still working on All Star, I fear doing Boss Battles with all 35 *shudders*

@Onimusha: I've tried for quiet a few hours today. Duon gives me occasional problems, but most often I handle him well. Golleom is the real pain in the rear for me now. Raquaiza, the Ridley's, the Hands, and (of course)Petey are all easy for me now(majority of the time). Porky usually goes down down pretty easy as well. This was with using Lucas the last few hours. I may go back to Toon Link, but it is nice being able to heal yourself in certain battles with Lucas.

I had 8 of the bosses down and my 9th fight was Golleom. I had 31% damage going in, and a spare heart for Tabuu, but Golleon destroyed me. So close I could taste it.

so you can heal yourself with Lucas?

 Hah, you could always take the easy way out and well set it on easy.

even on easy if you time the dodge wrong when final boss does red wave attack your dead 1hit ko ......

 Actually on easy you can usually survive one hit provided you have full health. Dodging them with sidesteps isn't that hard if you practice by replaying the Great Maze on Subspace Emissary. Timing is actually pretty forgiving the trick is to space out the dodges, if you do them too fast you'll get hit. If you can best Boss Rush intense doing the other characters on easy will be a cake walk. 

I suck at this game so I did Boss Rush on Intense with Charizard. His Rock Smash does unusually large amounts of damage to bosses and he's somewhat on the heavy side. Tough part is trying to manage dodges with such a slow character and Rock Smash itself leaves you pretty open. With Duon you'd pretty much have to hit him hard and hope is sticks. With Tabuu you can actually use Pokemon change to avoid some of his more annoying attacks.

^^^ You beat boss battle on intense already 0_O ? I only manage to beat boss battle on very hard so far. Damn I can only beat 5-7boss then die on intense never made it to Tabuu yet . The word failure is depressing :(

 If by already, you mean after failing it over fifty times or so, then yes, I already beat boss rush on intense. =P

I experimented with Peach a little earlier and she's pretty effective actually. Most of the bosses are so huge you can endlessly keep her airborn by using her side special move. (That weird butt tackle thing she does) Each time it hits, it'll throw you a little further up and you can spam it constantly to keep in the air. With Petey you never even have to go near the damn cages, just keep bouncing off his head, and with Duon you can easily get behind him where he can only use his spin move on you. With Ray you can constantly keep above his Iron Tail and Leer moves.

She can also float which makes spamming up smashes on flying enemies easier. Also if you just jump once and use the side special to get airborne, you can use her second jump at anytime to float away, and after that you still have her up special to recover even further.