Quicken should allow for mass deletion out of the pending downloaded transactions tab.
I keep getting duplicated transactions from having to reset my account for online services. The root problem of this is that Capital One Card Services keeps going crazy and I have to do this to keep it working. However, every time I reset it, I get hundreds of duplicate transactions in the pending download tab. I know I can accept all and mass delete after acceptance but that is a very annoying process to go through. It would be far easier if I could just mass select and delete in the downloaded transactions tab before accepting them.