DK has a huge grab range thankfully, so you can make some good spacing to go along with it and you're well set. He's fast too, so that adds more to your arsenal. Number one thing when it comes to running grab is to jump cancel the grabs. How you do that is that you press any of your jump buttons, and within fractions of a second, you press your grab button, what this does is basically the movement of a standing grab, while running. It cuts out end lag and I believe it has better horizontal range than a dash grab, but I think I've heard that the dash grab has more vertical, and maybe even grabs behind DK some.
So you've gotten the grab, the hard part is now over. DK's got lots of options from this point. Best thing is usually to F throw, which puts them into cargo throw. Now you can carry them around and do whatever you want. You want to either Cargo up throw into up air strings, or cargo F throw into Nairs or foward air, I'll get to kill options in just a second. A fresh Nair does 15 percent, which is a pretty hard hit. Usually if you catch DI right, or they don't know how to DI, you can usually catch two Nairs out of a Cargo forward throw if you can position and fast fall just right. Cargo up throw into up airs are what DK's known a lot for, because it can kill fast fallers/ heavy characters. StarFox characters, Sonic, Pit, Lucas, all the ones that are fast fallers are the ones afraid of this chain, because there's pretty much nothing they can do. And always remember to mix up DI with turnarounds, general throw mixups, the basic things.
Now then I'll try to iterate how to space well. DK is huge, which is both good and bad. Bad because it means he's a big combo target. Good because he has the mass to space pretty well. Best spacing move will always be back air because of how far out it reaches, Nair and ftilt are good too. D tilt, if you can use it smartly Fair works too. DK spaces really well, and if you mess up some spacing then shield grabbing is also an option to punish and reset if your opponent spaces bad as well.
Now then for recovery, this one can be tough. Sweetspotting the ledge isn't out of the question, but it's pretty close. You have to time it just right because there's no cancelling the move and dropping. You either have to recovery with some tricksies, or be straightforward about it and find an option with little to no punish chance. Tricksies being going for a platform possibly either landing on it, falling through it, or going for it, and quickly pulling a U turn away from it. Also, if you play a Mario, they're always going to be looking for the cap. So you can A: trick them into whiffing a cape, B: just get back onto the stage and risk a possible punish.
Edgeguarding, this can be easy or hard. DK has got an easy top 5 best horizontal recovery in the game, so as long as you don't get tricked into something, off the stage styling edgeguards are an option. Nair does good horizontal knockback whether the strong or weak hit. Back air always works well as well. Now for guarding the ledge, that's a bit more complicated. An angled or non angled Ftilt is never bad, because you can space it to where you're out of harm's way. You can space a Fair to where you spike them as they grab they ledge, DK's hands grow at least twice their actual size when he swings so they can hit below the ledge some as well as keep you safe due to spacing.
As for defensive options, always try to reset. If you can get out of pressure, do it and run away. Unless you can get a nifty shield grab, DK can't deal too well with pressure, he's too big and his weight and hitstun amounts just don't help you any. Run away and reset back to neutral is my best advice. Or if you wanna try and turn the tables you can try crouch cancelling. What this does is nullify knockback from moves, until you get to a certain percent. All you have to do is crouch, it's that easy. From here you have really only two options since you have to be fast. You can either throw out some fast D tilts to try and get some space and run away as I said earlier. Or you can do a jump cancel grab, it's fast and a grab, which is just what DK needs.
Kill moves are what DK has a plethora of. DK punch, need I say more? Get that badboy charges ASAP, because it does about 30 percent if fully charged and even if it's a hit at 0, that was a fast 0 to 30. Make a read, or a cargo U or F throw into the punch and you have an easy setup. I'm very certain it can be DI'd, but I can't remember all the scenarios it's happened to me. Unless on semi floaty, to floaty characters, I call this the StrongBad combo, you can cargo them, jump, Cargo U throw midway through the jump, then jump instantly behind them and Fair and you've got a pretty good shot at hitting them and boy do you hit them hard.I dpon't think it's guaranteed, but if you wanna be safe, do a cargo throw to Nair. It's not as strong but it hits really fast and it's still pretty strong.Stray hits are a bit difficult with DK, but they can work every once in a while, I suggest always trying a throw setup.
Last and definitely not least, counterpicks. I've gotten to the point of thinking that there are few matchup counterpicks, and that they're more of personal preferences. But here's my list of usual counterpicks/ desired stages. PS2, PS1, Dreamland, Smashville, FD, Green Hill Zone, Battlefield, and Yoshi's Island from Brawl.
I'm very open to constructive criticism as well as mentioning anything I left out, which very well could be a lot. Hope this helps you guys, thanks for reading! :D