Oh, the humanity!
That’s an interesting topic for discussion right there. It kind of flies against Trek’s core humanistic philosophy, for me, to say that there are such things are irredeemable people. Let’s say, even if somebody has the personality structure of a psychopath, as many do, if that person consciously manages their darker impulses and fights only to do good things, to help rather than harm others, couldn’t such a person be considered redeemed? By the choices they make in the moment? Doesn’t mean you write off past crimes; certain things must be atoned for. Yet each moment we can choose to be different. each moment we can be redeemed; whatever that might mean.
I found the Georgiou arc in DSC S3 quite affecting, right down to her returning to the Mirror Universe and realising she was not that person anymore. Her environment had changed her, for the better. That’s just the essence of Star Trek for me. Rather than just showing already perfect people, as in TNG, why not show people consciously moving from dark to light; there’s much more drama to be found there.