Wow, tough question.
I have the abrasiveness trait (people here may have noticed that; I'm trying
), and two of my kids have the do-just-enough trait to varying degrees. When I'm doing serious work, I do my absolute best, though I've learned to recognize which jobs are only worth 90% effort (they're usually trivial ones and of minor importance to an organization; anything for a client is 100% effort). So here's my perspective based on that introduction.
For me, the only way I can survive in a structured work environment is to keep my mouth shut when I feel my abrasive side bubbling up. I try very hard to pick my battles. It's not easy, and I can really only last about two years working for someone else before it starts to eat me up inside. This is why I've been mostly working for myself for the last 15 years or so. Right now I have funding to run a small non-profit, and am doing meaningful work and really enjoying it. Doing your own stuff has a way of bringing out your best.
If working for himself isn't an option for your brother, I sympathize, having been there. Again, I try to pick the things I'm willing to voice an opinion about, and try to let the other stuff slide.
Also, it's possible that his employer is being harder on him than others because he isn't doing his best. I've had underperforming employees, and it's very frustrating from the manager's perspective. You feel like you have to spend more time with them to get them to do less work, and if you leave them alone, it just gets worse. So you tend to get tougher with them, because it's necessary and because you're frustrated. Your brother may want to take a hard and honest look at his performance and ask himself if this idea applies to him (it may not).
I unlearned underachievement in college. I coasted through high school doing minimal work and still graduated in the top 10 of a class of nearly 400. I attended a challenging college, and at some point early in my freshman year, decided it was time to be serious. IMO, this decision MUST come from within. No one will be able to convince your brother to put in his best effort except him. It sounds like he wants to do that.
As for strategies, I personally just had to bite the bullet and get used to working harder. It wasn't easy, and it still isn't at times, but I told myself that I wanted more and had to be willing to try harder in order to get it. This is what I tell my kids when I see that they're trying to coast.
HTH.
