Often you will need the person to bottom out if they are stubborn. Your job is to control what that bottom is (not death, not financial ruin). Does he/she know that you can possibly leave? They are not valuing things properly anymore, so you have to jump start that.

I will speak out against professional help since I know many cases (anecdotal) where such help doesn’t work or reinforces the problem.

My own depression came out of entitlement. I didn’t know I could actually get sadder (which inevitably happened), and it bumped everything back into perspective. It’s a perception issue imho. You think this is as sad as you can get, well let me show you. Guide him/her through the shadow of the valley of death, and let them see the bottom.

Scared straight works.