I was a Union rep for decades... and I ran into a lot of these guys (usually women actually) over the years. I worked with them to keep their jobs, and to build more sustainable lives. Many times, these folks managed to turn it around, keep their jobs, cut down on their drinking or give up their drugs/abusive habits, but the success rate wasn't high, maybe 50% or so.
The first thing I would ask an employee who'd I'd been asked to represent was, "Do you like working here?" They almost always said yes, So my next comment would be something like, "Well then, you are going to stop doing this thing that caused us to be here today. Do you like this job enough to stop doing this thing?" They always said they did, but to be honest, I didn't believe a lot of them...
Most of these people had come from lousy homes, bad marriages, even jail... and I quickly learned that in most of them, there wasn't a lot to work with. Sadly.
But once in awhile, I'd get a real surprise, and a really rotten employee would turn into, not just a serviceable employee, but an actual leader.
So... I'm open to reclamation projects, but I'm not going to bet the farm on them.