DemandTools will get the job done

DemandTools was a great way to clean up a very messy Salesforce database at a previous company. It is an extremely powerful tool but takes some research before you're able to use it correctly. However, what it can ultimately accomplish is fantastic. When we reviewed solutions on the market (admittedly, this was several years ago), DemandTools was the only one that would manage all the tasks we needed complete.