However, that search took me to an example that I didn't recall, resulting in loss of life. I'll probably reference this story about the Therac-25 in the future as it hits on a number of clear software engineering failures:
-- https://www.bugsnag.com/blog/bug-day-race-condition-therac-2...
You can also chalk it up as a non software engineering failure because the sensor hardware is what failed first.
It's not very clear cut.
The multi-day 2003 blackout in the Northeast US states and Ontario, Canada qualifies in terms of impact (many billions of $). It was a systemic flaw with a software bug as a proximate cause. I think most major failures with high impact in a software-intensive system will sort of look similar: a software fault that cascades to the real world.
https://en.m.wikipedia.org/wiki/Northeast_blackout_of_2003
Other examples might be the various outages in airline reservation systems.
If you’re interested in this kind of thing, the archives of the Usenet newsgroup comp.risks are interesting (not sure if it’s still active).
In the realm of software engineering I don't know that we've had a catastrophic failure where the infrastructure costs of repair were in the billions or there was tangible loss of life. The biggest example that comes to mind was the explosion of the Ariane rocket because the software caused the rocket to rotate in the wrong direction so the ground-controllers executed a self-destruct... maybe pieces of a Tesla that crashed while on auto-pilot would be a candidate for physical objects we can hold in our hands to remind us that software bugs can kill?