Bad USB not recognized by Finder
When I run into this kind of problem, I first identify the device with:

diskutil list


(e.g., /dev/disk3 -- BE SURE TO GET THE CORRECT DEVICE OR YOU WILL HAVE DATA LOSS)

Then I use the dd command to zero it out.

sudo dd if=/dev/zero of=/dev/disk3 bs=8M


I hardly ever wait to completion, rather just a few seconds (maybe 10-15) and then press Control-C to stop it. This is just enough to wipe out everything at the start of the device that tells how it's formatted.

At that point, I go back into Disk Utility, insert the device, and repartition it, putting on a new formatted filesystem.