It might be a little late for this, but if you zip the save folder and email support@larian.com (or post/PM a Dropbox or Google drive link, etc) I can take a look at it.
It should be possible to either fix it or kill it by editing the data.000 file, or possibly replace the character data, making it an opponent again.
Teleporting Anywhere, via hex editor /
Reviving dead NPCs
