The thing that most immediately comes to mind is Cameron Kyle-Sidell, who recognized that the standard treatment protocols were over-intubating people for hypoxemia, and that overly high pressures of ventilators were causing damage. He faced a great deal of resistance within his institution at the time, and was quite controversial in taking his case to Twitter and Youtube. Since then, he's been vindicated, and protocols have been changed.

I post this because I think it's the exception that proves the rule. Dr. Kyle-Sidell is a physician of great perception and insight. For every one of him, there are no doubt hundreds of "hydroxychloroquine doctors" who peddle bullshit without scientific basis to the harm of their patients. But the existence of doctors like him does boost the "maverick doctor bucking the institution" narrative.

[1]: https://www.medscape.com/viewarticle/928156

[2]: https://elemental.medium.com/how-one-covid-19-doctor-became-...

Couple of them are described here..

https://drmalcolmkendrick.org/2021/01/27/does-lockdown-work-...

Under the heading "The damage inflicted by medical ideas"

MitoQ