The Absolute Worst.
The absolute worst action you can think of any kind, can not compare to reality of cutting off a family member. Especially, if that family member is your child.
Nothing compares to the love you feel for your children. So coming to the conclusion that you MUST NEVER speak to or see one them again is not an easy decision. It hurts. But for both parties sake it must be done. Take heed, that no one deserves to be disrespected and abused. Not child nor parent.