So, I work in an industry where huge amounts of money (read: billions) exchange hands on a daily basis and a minor mistake caused by a lack of attention to detail can result in losses of multi-millions of dollars.

Today, we had to let a junior employee go for a 2 million dollar mistake that could have been avoided if they focused intently on the task they were assigned to handle rather than playing on their phone.

They vehemently disagreed and were escorted out by security while profanely yelling the entire time meanwhile the senior guys on the desk (I.e, me) had to try and leverage relationships to beg to cancel the error to no avail.

Just wondering, what large scale mistakes have you made at work or have witnessed others make?