The first time I encountered ethical concerns was when a reviewer insisted on having his unrelated eight research papers cited in the revised manuscript. The question arises regarding the ethicality of such an act, especially when it is approved by the editor. What will be your course of action when you encounter this unwanted thing?
See the replies by Joseph C Lee and others to https://www.researchgate.net/post/Unethical_act_of_Reviewer/1 and two other discussions for which I indicated the links therein. But see also https://www.researchgate.net/post/What-should-author-do-when-the-reviewer-asked-him-to-cite-some-of-his-published-research-papers for alternative opinions.
Either do what they say or withdraw the paper and publish elsewhere. Arguing with journals never works :)
@ Dr Andrew Paul McKenzie Pegman, Thank you for your valuable recommendations. I have noted it.