Are there known examples of ex-McKinsey employees that are generally considered a force for good in general?

Jørgen Vig Knudstorp saved Lego

Peter Attia's book on longevity is really wonderful, as is his public discourse and research.

The best manager I ever had was an ex-McKinsey consultant. Extremely empathetic, super competent, good dude. I have not worked with him for years but still text him for advice, and he delivers. I suppose that there are people who left McKinsey because they thought they could make more money elsewhere, and people who left McKinsey because they realized they made a huge mistake working there.

Jeremy Howard comes to mind. The sheer good that fast.ai brought as free quality educational material feels enough for "good in general" :)

Tom Peters’ work on management excellence is generally well-regarded and he started it at McKinsey.

He’s also more recently spoken pretty aggressively about how he thinks McKinsey has lost their way as a business and become a negative force.

Not that well-regarded any more since his fabrications came to light.

McKinsey has absolutely stellar engineers and engineering leadership in its internal software teams, it's a gift and joy to work with them. Not sure about the consulting side though.