A big piece of enterprise software I've worked on did a full rewrite successfully. This was a long time before I joined, but the original product was written in

A big piece of enterprise software I've worked on did a full rewrite successfully. This was a long time before I joined, but the original product was written in Magik and apparently the only requirement was "make it work like magik" which I thought was pretty funny. It definitely was a success. Though on the same product I came across a mildly hideous half-baked attempt at a UI framework re-write. I got the story on that and it was definitely one of the time-wasting regret stories. Software is mostly just hard and expensive.