A big fat "Are you really sure?" confirmation box would seem to be the absolute minimum requirement here...

A previous employer had an “are you sure?” dialogue on Outlook’s reply-all button, you can script it up in VBA.

Didn’t stop people from doing it.

If it that dialog fired every time I clicked reply-all, I would start ignoring that dialog, especially if it was annoying.

You mean like https://youtu.be/pnBVIhiUd_g?

We're talking about a missile incoming. I think they move fairly rapidly; the response system ought to be rapid as well.

People are used to say Yes in a standard confirmation dialog. It would be helpful to implement something more complicated like pressing two buttons, typing "yes" to a clear question or solving a simple puzzle (ideally visualizing the outcome while solving it).

A common pattern, e.g. used by github when deleting repos, is to type something (e.g. the name of said github repo); not necessarily a puzzle, just spelling out the thing you want done.

typing “send sms alert” vs testing “do not send sms alert”. that way you’d have muscle memory for the latter, but you’d know what to do if you really wanted to do it

Putting the button behind glass.

At a military communications center I once worked at we had the EPO button positioned near the door so you knew where it was, and you could hit it on the way out as you evacuated. One day someone had a toolbag in their hand as they were leaving and it swung and hit that big red button ... and it did what it was supposed to do - cutting all the power to the room. Which ended up being a big hassle - they had to reload crypto keys and so on.

That very afternoon a plastic guard was installed over the button so you had to lift it first.

One of my jobs in a big computer room had the same big red buttons by the door for the fire suppression system. By the time I'd gotten there in the 90s, they already had plastic covers on them, and had since a similar incident early 80s.

Hey, they figured it out with fire extinguishers!