Dentist malpractice: what to do?

Did anybody had a success in filing a complain for dantist malpractice? Or it's better to just forget and move one?
*my apologies for poor grammar, English is not my native language.

So I went to this fancy English-speaking doctor in Hiroo with a two cavities in between the teeth (we did an x-ray to confirm), paid more than 17万 for treatment and was happy they pain was gone. Pain was not super strong initially, rather on a side of discomfort.

After few weeks I still had a discomfort – which I thought was caused by poor filling adjustment, so I came again, paid for a visit, he adjusted the filling. Then I still had this discomfort with a sensation that something stuck between the teeth and pain becoming worse after the food. No reaction to hot or cold, never had it. I came to him again and all he did – was to adjust the filling again.

So, Dec 23 – treatment, Jan 24 – first complain and adjustment, Jun 24 – second complain and again adjustment.

So I went to another doctor, who did an x-ray and confirmed that actually one cavity was not treated at all, that’s the reason I have this discomfort.

Now I’m at the initial Hiroo doctor’s office and he finally told me that he didn’t treat one of the cavity as “it will influence the tooth structure and he had to remove the big part of healthy tooth”. Like WTF?
It looks like a total scam to me. He didn’t tell me that he will leave one cavity untreated and who even does that?

Now he says that he can do the full treatment with no fee, but honestly there is no way I’ll sit in the chair of this doctor again. So I asked him that I need a letter of recommendation to a university hospital and a 50% refund, since he did only half.

He refused to make refund and now telling me that I need to pay “recommendation letter fee” and “copy fee” to get a copy of my records.

So what can I do in this situation? Beyond leaving him one star review on Google maps.