Chernobyl is the only nuclear disaster that makes me thing "hm, maybe really nobody should ever build nuclear power plants" and it occurred under a dictatorship. There have been significant disasters (Fukushima and Three Mile Island) under democracies but both of those are pretty tame compared to the ongoing harm wrought by coal and natural gas. Even if you just restrict it to direct health effects of their pollution vs. all negative health effects from Fukushima, at worst Fukushima over its lifetime likely cost fewer lives per megawatt-hour than an average coal plant.

(Of course, things like solar and wind are still generally preferable, if you can store the power effectively.)