Generally the smaller a nuclear explosion is the greater the danger of radiation relative to the blast. The bombs at Hiroshim and Nagasaki killed many people via radiation sickness. For modern strategic weapons if you're close enough to worry about that you'll have already died from the blast.

Of course fallout, especially from explosions on the ground to destroy hardened bunkers, silos, and sub pens can generate terrifying levels of fallout. It's just the prompt radiation from the explosion itself that usually isn't a concern.

No (nuclear) fizzle necessary. Just blow apart some abused Cobalt-60 source by conventional means, scrapped from medical or materials testing equipment. Imagine the scare. Effective area denial.