I recently went to one who failed at the first step of the flowchart :

"Is the patient a woman."

The answer was no, but she prescribed a useless medication for a condition I didn't have, and didn't adress the actual problem.

Conceiling power level, but it was, to pick a comparable example, as silly as insisting it's breast cancer when your patient is a male, complaining about chest pain, and the tissue samples are not cancerous.

Some GPs make extremely stupid mistakes.