Simply replace the unfilled areas such as "__" and "_[date]_" with your information.
Dear [manager or human resources rep],
Please accept this as my one week notice of resignation. My last day will be [date of last intended work day].
I apologize for not giving a full two weeks notice. However, I am so unhappy and uncomfortable with the way I am being treated by [name of person or persons mistreating] that I do not feel that I will be able to make two more weeks without an incident occurring. In fact, I feel that working one more week will be trying for me, but I don't feel like leaving with no notice at all is right.