>Even if deregulation increased nuclear deaths per watt by two orders of magnitude (which I strongly doubt!)

Why doubt it?

Chernobyl alone was very close to causing millions of deaths. The actual accident released only about 5% of the core, but had the graphite fire not been extinguished, places as far away as Scotland and Scandinavia would not be able to grow enough edible food within their borders for decades. Europe would starve. Leukemia cases would be in the millions.

The exclusion zone around Chernobyl would be hundreds of kilometers instead of 30.

If the ground water barrier had been broken - which was likely - the ground water for tens of millions of people would be poisoned for centuries.

The only reason to doubt it is that two orders of magnitude is probably not enough.