Kaido and Whitebeard just aren't. Both would be Dragon threats in OPM, but that doesn't mean anything.
Jigen is and Delta isn't.
Byakuya and Kenpachi maybe...? I don't quite believe all the ridiculous speed calcs that come out of Bleach fans. They both definitely have the cutting power, but Saitama is fast so the speed part matters a lot. Both could potentially one shot Saitama but he could do the same.
Both Godzilla and Aldoron are probably too slow, but have far better durability than anyone Saitama has fought so far.
Raditz and Nappa are physically some of the weakest people on this list and don't stand a chance.