One of the most physically powerful characters in the game, it's hard to get the upperhand on Donkey Kong at close range.
If you have a high status bar and he hits you with a giant punch, consider yourself gone. Donkey Kong has always done well against Fox as he can't reflect any of his moves. Though Donkey Kong's biggest weakness is his range. You won't be picking off opponents from long range unless you have a good item.
His final smash now has him trading his bongos for a pure beating of fists. I didn't like this final smash too much as you really have to be right at the foe to do anything. All final smash powers had been diluted for Ultimate, so even if it does land, you might survive.
When Kirby takes his power, he gains the ability to use the giant punch. While some of Kirby's powers are the weakest, he got Donkey Kong's best.