Well, this one was very satisfying.

When I resigned from my previous job, there was this one last task I had to finish. The task was to implement an identity and access management system that would work across three different platforms they had. I used to work on one of them which had nothing of the sort but the other two had something of their own. Here lies the kicker, it had to work with existing authorization system in other two platforms. After explaining multiple times why that is a bad idea, I gave up. I created an interface, no implementation, documented how the interface was meant to be used and got the hell out of there.