I do not have any particular PD to blacklist. So far the PDs I met are all quite professional and knowledgeable.
Here is a guide on whether a PD is good or not, in my own opinions:
1. Ignore your questions and not willing to take effort to explain.
2. Will prescribe antibiotics for your kid for almost all illness, even slight flu.
3. Being rude to your kid, e.g. cause injury during jab injection.
4. Not detailed in examination process, e.g. prescribe medicine soley based on your own description with the PD