Tabuu In boss battles mode I can never beat him because he does that one move where his kill you automatically... help...

I'm assuming your speaking of Taboo, when he does that move where a large red ring pushes you off the stage. (Just here to clarify for others, I really don't know what to tell you...)

The 3 RROD's?

If playing as Charizard (Or just PKMN Trainer in general) Down+B

anyone else, Sidestep thru all three rings

EDIT:    I still have yet to beat him on intense yet, only Very Hard. 

I'm not sure because I haven't tried, but I thought long and hard about it in preperation for boss mode and I'm guessing you have to air dodge, or parry (defend+down) in order to avoid it. But I'm not sure...heh...that wasn't helpful.

Just like LCEC said, side-step the 3 red rings of death. Hit the block button and when each ring starts to expand outward hit down(while still holding block the entire time). Once you do it the first time you won't have any problems doing it afterwards.

You can do what I do.

Kill him before he gets the chance to do it.

personally - i dropped the difficulty level down to easy.

I'm pretty sure he's talking about the gold clasps that grab you and fly you off the screen with zero notice.

What I do is keep jumping around constantly the entire fight, giving you a chance to dodge if he summons it.

I am trying to beat it on normal for the trophy... I only beat it on easy because I killed him before the triple RROD...

 same :)