Ok.. If you make it to Tabuu on any mode, don't get too nervous and change your basic strategy from before. Attack-modesty is still key. Also, facing Tabuu with anything more than about 35% damage is really pushing your luck in defeating him, especially if it's your first time making it to him.
So.. Tabuu: Though probably easier with other characters, Tabuu is unfortunately pretty tough to beat with DK. Stick with it though, it’s doable, I swear! Whenever he’s just warping from place to place, just stay where you are and spam DKs normal up-A attack for the best chance of getting a hit in. When he’s stationary after an attack, depending on how close you are to him when he’s done, you can usually get one or two over-A smashes in (two if you’re close), followed by one or two quick standard A punches. Like all the bosses tho, it’s critical to not get greedy--give yourself time to get back to the middle of the stage to dodge his attacks. When in the air, use the forward-A (Or in some cases, up-A) to hit him. Also always be aware where he ends up, cause if it’s right next to you, he’s about to hit you with that rapid-punching combo, so make sure you do two roll-dodges behind to get away, then attack him from behind with over-A smashes. Like Porky’s rapid-slash move, always pray for this one, as it’s a great way to inflict damage.
--Move Strategies— So many, that this one won’t be in written paragraph form! Explosive Warp: Just roll dodge at the exact time he warps each time. You should be damage free. Red Rings of Doom: Now I got hit by this once on Very Hard at it gave me 49% damage and launched me fairly high, so I’m assuming that on intense it’s probably gonna kill you no matter what. Thankfully it’s pretty easy to dodge, since DK has quick roll-dodge recovery. Just go into shield-mode right as he’s readying the move, and roll when appropriate. There’s a little bit of time between each one. Just don’t get antsy and dodge too quickly! Golden Whip: Deceptively hard to dodge, as it comes quicker than you think. When he busts out the chain, just double jump and immediately air dodge, as his whipping motion is basically too quick to see—it’s all anticipation. Head Lasers: Double-jump and up-B into his enormous head. I like this better than sitting there and doing up-A smashes as you’re going to take way less damage this way. Giant Horizontal Arrowhead Spear.. thing: Just air dodge. Pretty Simple. Same goes for the spinning boomerang (remember on the way back, of course). Altho remember that on Intense these moves are much faster than their lower-difficulty counter-parts, so be ready! Ivysaur-like Seed shooting: It’s pretty easy to see this one coming, so if you can get under him, then great! Hit him with some aerials. If you end up further away tho, you’ll probably get hit by a couple of them, but as long as you’re jumping and air-dodging away, it shouldn’t be too bad. Energy-Wave: Similar to Mario’s final smash. He’ll point forward with a single fist for about a second, giving you time to dash then double-jump and up-B up and awayyy from that attack. 100 Tabuus: The move where he shoots out a lot of clones from him. Consider yourself unlucky if he does this, cause he rarely does, and its pretty hard to completely dodge. Constantly jumping and air dodging is your best bet for this move. Energy Beast: The one where he mounts some beast and it shoots a laser from its mouth. Just double jump and up-B above it to be safe. Pretty easy to dodge.
Phew. =p Well, hopefully this helps some people that are frustrated with boss challenges. I too once thought that I'd never even be able to beat it with all characters on easy, let alone on Intense, and was angry at the game for making it hammer-immune

BUT, after you get over the intimidation-factor, and get into a good groove of attacking and retreating, it's not too bad. Sorry for those who don't like DK, but I really don't have any good specific strategies for other characters for the harder modes.