It was hard to decide what I hated most about the project. The mind numbing stupidity of it. That fact that managers had allowed this single point of failure, and then let the guy leave. Or... that it was all a fictitious dance, pursued because spinning off their trading operations, would get them millions in tax subsidies.
After he left his job, some poor soul had to inherit his massive collection of VBA scripts, which more or less automated his day-to-day work. I think he showed the new guy what buttons to press on his spreadsheets, but I can't imagine he understood any of the Excel-fu my father had done. The legacy architecture that is tied to Excel in all sorts of businesses.. it's crazy.
The worst part is that it's not something that can be solved with an external dependency on some new startup - that would just add another layer we'd have to go through in the error cases, which would be numerous.
God, I wish I could share some of the files we've received. I cannot conceive what sort of monster would write a data exporter that would produce these unreadable things.
The hardest ones to work with were the mom and pop shops who suddenly had some success on Amazon and came to us after fulfilling out of their garage for a year and a half. Try telling a semi-retired 60 year old electrician in the middle of Iowa that the file he sent is worthless because none of the product codes match what you have, especially when once he closes the file he doesn't have any idea where it is.