Chaingrab or not, I'd say ZSS is even with King Dedede (maybe a small tip in ZSS's favor, nothing significant).
DDD's worse matchups that aren't hard to pick up for DDD alone are probably
Olimar and Falco.
Olimar you basically spam him with side-b.
It takes an hour of learning what each Pikmin does on the boards then an hour experimenting with them and putting them to good use, and about 1 week playing with him to get it down.
If you are good at DI, remembering little nitpicks, and good at camping (so Samus means probably yes), then yeah.
Olimar is a very good turtle character and DDD gets wrecked by that.
At one point I used to use Olimar as a DDD counter when I mained ROB and Snake equally but then I got enough practice and I decided three characters was too much, and DDD wasn't a problem.
This process eventually weeded out until I was only using Snake.
lol