I'd like to put a bit of input on matches not really covered yet, or matches i dont really think we're noted accurately.
Capt. Falcon - This poor soul gets out prioritized on almost every approach he has. An extremely nerfed version of his former melee self. He can however combo DK decently, good thing you can combo him better. Also watch for pivoted f-smash and forward-b from him, even so your approach should beat his forward-b as long as you didnt do anything to laggy as in wiffing a u-air or f-air, which you shouldnt be approaching with to much anyway. His only aerial that can kill is his f-air which should be pretty hard for him to land considering the hitbox and the low priority, his f-smash,d-smash, and his u-smash which he can run and slide with can kill, be careful. DK's b-air and u-tilt beat EVERYTHING HE HAS, not to mention Donkey Punch, mainly because, it beats everything. Difficulty 3 at best.
Sonic - From what i have seen in the meta-game of sonic as well as the sonic players ive faced, this looks alot like Capt. Falcon all over again. DK's Bair and U-tilt reign over his whole moveset, if he starts charging anyone of his B moves, face backwards and punish with u-tilt, if you have Donkey punch stocked: blow his face off and onto a game thats actually made by sega. His kill moves are pathetic especially due to DKs weight and his combo's are mediocre. His speed can be a problem just dont let him pressure you, you have more range, pressure, and KO potential, than he ever will. His f-air can be an annoying pressure on your shield, due to the multihit, it can poke through the shield, try to powershield this or just challenge it, it doesnt have much priority. Also difficulty 3 imo.
Jigglypuff - Jigglypuff mains around the world screamed in unison when they found out how nerfed his moveset was and how bad he molds with the new gameplay mechanics. His WoP (Wall of pain; a series of b-airs usually taking you off the stage and to the edge of the screen or off the screen to your death.) isnt really anything to worry about due to the new airdodge system. Jigglypuff also had his frame enlarged, making him a bigger target, not to good for him considering the priority on his aerial moveset now as well as spamming b-air isnt to practical due to diminishing returns. His rest was also nerfed to an extent, instead of being an excellent KO move that can destroy you at 20%+ it now kills at about 70-80%+ given character weight and DI. Again, this characters entire moveset can be beaten by DK's b-air or u-tilt. Also given jigglypuff is a lightweight he dies easily in the 70%+ and he should be killing you around the 150%, not so good for him. Difficulty 3
Lucario - We all know the high risk / high reward factor lucario has: the higher his %, the harder he hits. The problem for lucario is he is a light character, as well as DK is abundant in hard hitting KO moves, he will most likely never live passed 100%, with that being said, he isnt going to be able to get exceptionally powerful, add in DK's heavy weight and lucario now has a serious problem. Lucario does have some pretty good combo's, but for the majority of them they require him to be at a low percent making the combos not exactly good in the damage department, they are mostly just fustrating. If lucario is trying to camp with small aura spheres, you can easily hit them with jab, f-tilt, u-tilt, etc and make them disappear. Try not to be to predictable with your heavy hitting moves (Donkey punch or any of your smash attacks), if he counters them, you will pay for it. Alot of lucarios think and know their d-air is almost unbeatable when you are below it, however if spaced correctly, DK can U-smash and beat it, dont challenge it with u-air it will always lose. Difficulty 4
Marth - I find this match up extremely boring, you need patience to overcome this fight. First off in aerial terms, marth will be approaching with f-airs, and in DK's aerial terms, he will be approaching with b-air. Where this gets boring is the fact that when these two find themselves in the air, they for the most part tie, you are both delt the damage accordingly. For the most part, i do believe DK has a slight advantage in this match up, and the advantage is KO potential. DI is exceptionally important in this match up. If he is chaining f-airs on you DI down or away from him, odd concept i know, but it'll limit his f-air chains and might save you from a d-air spike. Having momentum in this fight is very key, he can pressure well with f-airs and forward-b, a bad roll or paniced move can cost you a stock. Watch shield grabs marth can space outside of your grab range quite easily, as well as dont be to hasty to grab him out of his forward-b chain, be patient wait for it to finish. Difficulty 4-5
Olimar - I wont lie here, im completely biased in this match up, i indefinitely think DK has an extreme advantage. For the most part from what i can see with peoples complaints is just inexperience with the match-up. I will admit though his grab range is quite pesky. Ok for the most part DK's moves kill every type of pikmin, but the purples in 1 shot, if he is hurling pikmin to rack up damage, kill them unless you are in mid-combo or mid-pressure, either with an u-tilt, u-air, or n-air you dont want to be taking unnecessary damage. Learn and remember what every color of pikmin does, it'll help you with the correct approach, the ones you really need to look out for is: yellow, purple, and blue. Forward-b is your best friend here, ive seen other DKs talk about it so i know its being used however:
http://www.youtube.com/watch?v=8FikvqC3n-8 what i do at 0:53 is: Instead of doing short hop double b-airs, i throw out the first b-air and instead of landing the second one i forward-b (pretty explainitory), what this does is gives you some height off the ground where a shield grab would wiff and boom their dumb *** is stuck in the ground. Where this comes in for olimar is under shield pressure, due to there long grab reach they will think they can grab you out of double b-airs, or they will try to d-smash out of shield, with this approach as a factor they will have to think twice about what to do while being pressured. Also gimping his recovery is entirely to easy, you can do it as early as 20-40%. Diffculty 3-4