[brucethemoose2]

The initial fission stage is the "hard" part of a nuke, but the subsequent fusion stages are much easier to scale up. Arbitrarily large nuclear bombs are theoretically "easy" to make by chaining increasingly large fusion stages one after the other, as they aren't limited by expensive fissile material.

https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-bi...

Hence scientists extrapolated nukes really could end life on Earth, and in a slightly different reality than ours, they may have.

[roywiggins]

It would be really, really hard to kill the bacteria and Archaeans that we've since found hiding deep underground. They're long way down and would barely notice.