So this is a bonehead move I know but I need to get some help fixing this. First for the laugh I have a map/reduce script that uses a saved search of fulfillments and creates a record for each serial number on that fulfillment then opens the fulfillment and checks a box to make sure I don't rund that same fulfillment again. Well, I set it up and ran it but.... one of my fulfillments in the past was locked. So, every 15 min for the past month we have been creating 1000 records. I now have 1.8 million records I must delete. I have a mass update script that is running but it sure is taking its time. Anyone have a good idea how to quickly delete 1.8 million custom records.

Use a search for the ones you need to delete and use a MR script again. If you have more theads it will make use of them AFAIK Mass Updates single theaded