OK, so let's be clear: you tried to update the system when the battery was low and ran out of power part way through a system update. Correct?
So the most likely answer is that you ran out of power part way through updating the ROM, with the result that your android OS is corrupt. Could be worse - if you'd run out of power part way through updating the bootloader you would have a true brick on your hands. Seriously, do not try updates when your charge is low.
So your only real option is a ROM Update Utility (RUU). That's a Windows app that will reflash the phone over USB. But these things can only update your OS, and also depend on who provided it (so region and carrier). Now this is the HTC One (M7) forum, and you have a different device, so most people here won't know much about your phone. But if you can give us that information we can try to find the update package you need.
In the meanwhile, if we can get it working again will you please promise that you won't try system updates without power and with low charge again? I think it should be obvious why this was a bad idea.
