Hm, guess it's my turn.
Let's preface this with some of my earlier DK exp.
We can ****ing buttrape DK when he's on the ledge above 100%. He's so massively limited there, that we can throw a short egg, and the only real way he can avoid it is by dropping to regrab the ledge (+1 ledge count, yay time outs), or by an airdodge if he's jumping up. The thing is, is that we can punish an air dodge pretty well, and even if he ledge drops > DJAD, he'll probably land and get hit by the egg anyways.
Naturally, DK can get off the ledge, but you should be pressuring his *** all day there. Don't let him off easy, every bit of damage you put on him matters a LOT.
All that was from my first match against DK in tournament. Since then, I've played Will/Cable, who showed me that we didn't **** DK on the ledge THAT easily, although they still really hate it. In fact, they both hate the MU a lot, and I hate it too. Because it's scary as ****.
DK kills SO early that you need to be very careful about making stupid mistakes against him. A stupid mistake can cost you an early stock, which is bad, since we have some trouble outright killing DK.
Generally, you'll want to camp the **** out of DK until you can get in or get some momentum going. Egg toss at long range, dodge his Bairs. Either usmash them or pivot grab them. Just be VERY careful, as a smart wavebounced Headbutt of DONKEY Punch will **** both those options. And that's baaaaaaaaad.
However, when I think about the times I've gotten hit by those things, they're really only used when DK is like, on top of you when he's in the air. So just Usmash, and it can possibly beat both options. I don't remember when the SA is on the punch, but I'm pretty sure if you hit him early enough, you'll be safe. Otherwise, get that DI ready.
When you do hit him with something that's not an egg, follow it up. DK is susceptible to juggling, due to having a crap Dair. Just make sure you're not level with him and make sure that his back isn't facing you, and can pretty much destroy him. Don't be afraid to reset though, forcing things too much can only get you punished, and he can punish you with death in the form of a wavebounced Punch.
As far as gimping him goes, it's pretty hard to do unless you force him into recovering low, which is rare because most of our moves are pretty DIable to the top, except like, Dtilt. Dair works, but don't get footstooled out of it. Fair spike can work if your spacing is good, you need to be above him and abuse the range, so it's tough. You can set it up by Dtilting him as part of your ledge pressure, though.
I personally feel like we win 55:45 to 60:40, at top play. We have the options to avoid everything, but DK's punishes are pretty **** brutal. Just make sure you don't do anything stupid and you should win.
If you play too sloppily, this MU is baaaaaaaaaaaaad for us. You need to be precise.
For Celes: DK beats our HA pretty early. It's scary. >_>