Reuse USB after Cubic Image

I successfully created my Cubic image and created a startup disk on USB with Ubuntu Startup Disk. It created an ISO9660 partition, an EFI partition, and a third large partition of ext4 space. I wanted to format the unallocated space as NTFS so I could use it for storing files. Upon formatting that third partition, the liveusb would fail the filesystem check and not boot. So, in the meantime, I decided to recreate the startup disk. Ubuntu startup disk cannot write the image. I've tried deleting all partitions with fdisk, disks, and gparted. I've formatted the usb in windows using diskpart. No matter what I do, it seems there is some information on this usb that I can't remove, and nothing can read around. My EFI BIOS still sees a boot option for this USB which should no longer exist. Does anyone know how I can make this USB fully usable again?