After the return of my manager, I was tasked with helping the HR department, which had just become part of Decision Support. In this department, a database had been created many years before. Over time this database that was created to allow them to answer questions more quickly that the DBAs had been able to deliver, became a production database. This was despite all of the HR advisors/analysts, plus other people with HR, having full rights to create, modify and drop objects, and insert and change data. As you might imagine, this had led to various problems in the past where a report might suddenly stop working because a table that no one remembered about was not updated with a required date, or even worse, had data removed from it.
Over one year (which included some parental leave for myself), I helped to analyse and migrate or drop over 2.200 objects. At the end of the project, not only were we successful at creating a stable environment, we had corrected some significant issues with the data, and migrated all the reports (Microsoft SQL Server Reporting Services and Tableau) to using this new data source, with no-one noticing that anything had actually changed in the back-end.