I had a little chuckle at your worst nightmare, I wanted to say the same thing ;)
Ok other than Friday deployments, my worst nightmare is when I'm pressured into releasing features fast and not carefully. That is, the product owner expects features X, Y, Z by the end of the day, and I know full well that leaves zero time for writing unit tests, zero time to manually test each feature in enough real scenarios and zero time to care about my code linter screaming at me for writing terrible code.
That, or being told our project fails in IE8 after going live and that it needs to be fixed asap, when all along the acceptance criteria stated we only needed to support IE11...