@diversola
At worst the device should only be 'soft-bricked' even though you interrupted it while it was self-loading the new firmware from the GCD file. In explanation, GE works the same as WebUpdater. That is, it loads a GCD file to the device but the fw is not immediately updated. The update happens on next boot after disconnecting from PC. The GCD is like a self-extracting EXE file which is executed by the the device itself to then flash the appropriate regions of the device with the new data which is different to the way Updater.exe directly flashes the fw's BIN files from an RGN file or the way individual BINs are flashed by Ldr.bin using SD method.

So it shouldn't be 'dead' now unless it had a failing flash chip when you bought it and the chip has now collapsed. That kind of hardware fault can't be recovered by software manipulation but that is the less likely cause, probably it's just a firmware ('software') mess-up. Take it into a pitch-dark room or cupboard and check if the screen glows faintly on pressing the power button.