Everything Dedede does is easily punishable though. I spam his air normals, of course, but even those are slow. They're great for counter edge guarding, and his recovery is also great. His up+b is ridiculously punishable, and has a long wind up so that it is easy to avoid getting sat on. His spike balls can be knocked back with ease, and all his ground smash attacks have a horribly long wind up except maybe his down smash. His ground normals are pretty fast though, so its good to keep an eye out for that.
If its worth anything, I never use his up+b except to recover because I believe it to be his worst move. It locks you into the animation, and after landing the stars dissipate which makes him open to a punish. If I want to go airborne I use his already great jumps, that way I can spam normals if someone approaches me or land on someone with a forward+air or down+air.
Overall, I think most characters are pretty OP when you learn how to play them correctly. That's what makes this the most balanced Smash in the series, IMO.