How do I delete a profile in XIII? There's been one I want to delete, but I can't find the option in-game and I can't find the file.

Locate yor game installation folder. In this directory search "Save" folder. Profiles stored there.
But, if you play thru gog client - game used cloudsave. If you don't want profile to be restored by cloudsave - start the game, minimase it, delete profile from save folder while game is minimased. Quit game after deleting profile. Cloudsave synchonize and delete profile in cloud, then start game again. No profile in game. You can start over again.

Sorry for my English...