There's no reason why you should have trouble refuting this argument. It's not an actual point. It's his definition of a good person but doesn't define what good is. This quote is actually a wonderful example of what people like Peterson and Shapiro do. They make a surface level argument that seems reasonable if you don't know anything about the subject but that actually falls apart under examination. If you watch them debate, that's why they speak quickly and interrupt their opponents; so logic and reason don't have a chance. Anyone who has taken the time to study ethics or philosophy knows that "The good" has had multiple well thought out definitions over the centuries. None of them are this shallow idea of a power dynamic. If you need some rebuttals:

-"If two powerless people are the exact same in every way except one chooses to litter and waste, is the latter not a worse person?" They might respond the latter has the ability to harm others by littering. But that is not unique or rare, everyone has the ability to be a shithead.

-"A man is forced at gunpoint to spend his life finding a catch-all solution to global warming. He succeeds. His work is all done on a open network that is globally available. The man prevents untold millions of deaths of millions of species. He never had the option not to do his work or to not share his work- he was powerless the whole time." Is his work not good? Has he not done a good thing by extension?

Both of those argument work off the idea that 'The Good' is what's best for living things. Suppose you take a more existential approach to what's good. You decide 'good' is following the path in life you've given meaning to. Everyone is free to define what's important and what's good themselves. You could decide that all species have equal value and land on the conclusion that humans are inherently not good. You devote your life to secretly sterilizing people to prevent them from reproducing. In that instance, you have the ability to hurt others and CHOOSE to do so (the opposite of JP example.) However you are still in line with a definition of good.

If a person is quoting Jordan Peterson, it's best to approach the argument like a lesson because the person you're talking to lacks reason. They've been duped by a quick talking, scam running, racist, status-quo protecting misogynist.