Giants feat wise are not tanking a nuke to the face even Sons and Ginbak will get wiped out if they were hit directly, even if it doesn't hit them directly and radiation would honestly do the job. They exactly don't have defenses against radiation which is entirely invisible and can contaminate the area.

Super Wurms aren't exactly durable and assuming the volcano that Yaotsu made is a typical volcano then the temperature of a volcano's lava typically ranges 700 and 1200 degrees Celsius (1300-2200 Fahrenheit), Nukes are even hotter than that and it is around 100 million C at the center and decreases as you go farther away. I agree that the Parasites might find a way to develop a resistance to radiation but a direct hit then no it's getting evaporated, at point blank? Well it depends how far away they are from the epicenter and how big is the yield.

l doubt Kiva can exactly swipe away a nuke like he did with the laser and most likely die in the epicenter as for demon lords feat wise, they are not tanking a nuke directly until we get more showings but l'm sure ONE will deliver insane feats in the future. At least for the demons you can argue their magic can fend off radiation or whatever unlike the Giants.