Is slandering someone's name and treating them like garbage abusive?

Yes it is verbal abuse. I don't know if this "someone" is a mate or friend or perhaps a family member. If they are damaging your reputation and it could involve losing your job you can seek legal counsel and sue them for "Defamation of Character." If you don't want to go this route then handle it by dumping this person and get on with your life even if it's a parent, sibling, husband, wife, etc. No one should have to take this sort of treatment. You are in control of your own life! Good luck Marcy