It's hard to get through to an adult with their decades of negative reinforcement.
Yea I know that one, I've got a couple of friends who like to put me down.
Yet I know I'm not the one with the "problem" it's them.
One needs to make me look dumb to reflect others away from their lack of success.
The other because they have no confidence in themselves.
However I also find karma isn't just an eastern concept, other people will notice and will often react.
For example, if you're in a cafe and you get a very loud public critique about the way, or what your eating.
The waitress might get a little clumsy, your friend gets wet and you get a smile
Yet I don't give up on them, I know - like you - the more crud someone gets the more stronger they are.
You can cope with stuff they'd never be able to. Usually without even thinking about it.
Plus you have the ultimate sanction. You can ask the question "does this person add value to my life".
If you choose no, then (sometimes) you can cut that person out of your existence.
Yes it's not always easy to do, but when they are sitting alone crying into their beer, you'll be the one enjoying life.