Like with Mario, my main problem with Donkey Kong is that his personality is off from how he’s portrayed in his home series. I get the references to Donkey Kong and the older games where he had monkey noises, but they seem to be used at the expense of how he’s currently portrayed, which can make him seem like his character is reduced to just being an ape sometimes. I also kind of feel like the monkey noises will be incompatible with his new design so the next game is likely to have to voice act him at the very least.
It's not just the lack of voice acting though, it’s also little things like him having a face of pure rage during his most powerful attacks, which is kinda in line with how he is in Donkey Kong Jungle Beat, but that game was focused on making the character into a force of nature, which isn’t quite the vibe he has anywhere else. Given how he acts in other games, I think a more mischievous expression makes more sense here. Also, the taunt where he beats his chest should be less of a posturing gesture and more of a joyful cry to hype himself up.
Moveset wise, my only problem is with Headbutt. It’s boring and only situationally useful. If they replace it with something else it would probably be an upgrade. One thing that’s commonly said is due to his association with barrels, he should probably have a move that involves one, and I agree, though I’m not picky on how this is done. I’ve seen (and made) suggestions like a projectile where he rolls a barrel on the floor, a command grab where he stuffs opponents into a barrel, or an up special where he launches out of a barrel cannon, and I’d be happy with any of these ideas. I’ve also seen criticism of Giant Punch, as it is just a big punch, and I guess I wouldn’t be too sad if it was replaced, but I do think it fits the character, as it shows off his raw power, is unique as chargeable melee attacks are quite rare, and so satisfying to hit the fully charged version, so I personally quite like it.
I also think the fluidity of his movement could use some work. There is only so much you can do here because a character like him shouldn’t be speeding around the stage, but I think adding the jump canceling ability to his roll would help a lot. I’m not sure allowing him to fling himself across the stage with a roll jump would be balanced, but I do think it would be interesting if they made it work similar to how it does in Donkey Kong Country returns where you can roll off ledges and jump cancel the roll in midair. This could allow Donkey Kong to mixup his movement, and would be a boon to his edge guarding ability. If nothing else, I think the ability to jump cancel his roll would allow for it to become a more central part of his gameplan with it setting up combos at low percents and just feeling better to use in general.
Also, this is more of a personal thing, but I find it so weird that Cargo Throw is forward throw and not down throw. I feel like it would be more intuitive as a down throw, especially since it’s almost universally a combo throw at this point.
All things considered; I think Donkey Kong is mostly complete. There’s a tweak I’d make here or there, but most of his actual problems are audio/visual. This should be a character in his element, ready to bust some heads, toss people around like ragdolls, and react humorously when things go wrong. For the most part though, his personality is just…being an ape. A move involving a barrel wouldn’t go amiss here either, whatever form it would take.