If you have ssh over wifi hack installed, it could be possilbe to connect over wifi and delete installed files manually.
If you don't know which files update contains, use kindletool for extract the bin file.
If you haven't this hack installed, then I don't know, if you can connect to usb user storage, but if so, put there ENABLE_DIAGS and again, connect over ssh and delete installed files.
If any of this option won't work, try way described here
(But careful with this !!!)
https://www.mobileread.com/forums/sho...3&postcount=45
which is similar to wiki:
here.
There is also something about delete "Need repair",
but in many cases you need usbnet. And I think you need to delete file from bad update first.