Tree mulcher?
Lock the mother in the closet/pour gas on her and start a fire:
BUT......in our modern day society we need to rehabilitate such an individual so he/she can become a productive member of our technologically advanced civilization. They probably had parents who didn't hug them enough or tie their shoe laces every time they came untied. How could you possibly fathom harming such a gentle creature!!!! He needs OUR help.
*vomits in mouth*
Okay back to reality..... String said person to a tree......peel their skin off, pour honey on the muscles....and let animals, and insects eat them alive. I think this would be a fitting death.