What are some worst-case scenarios in your industry?

A while ago went through HAZOP (hazard and operability) study, first step for building a safety system, which is electrical or electronic programmable device to protect people from machines.

One hazard that they came up with was literally condensed down to "operator accidentally sits on mouse, kills 20 people".

It was a bit (as in shitloads) of a long bow, but we adjusted design accordingly.

Healthcare technology - medical record mixup, wrong medication/dose recorded, ignorance of certain racial medical concerns i.e. Glucose-6-phosphate dehydrogenase deficiency, etc.