Nuclear: there are many ways to estimate the amount of victims (long-term, all ailments...), leading to a huge interval of values.

"Fossil fuel or nuclear" is obsolete since renewables became pertinent. Moreover our current capacity to deploy useful nuclear reactors isn't convincing.

'Our world in data' retains the Banqiao case. It is somewhat debatable: https://news.ycombinator.com/item?id=32492422