Now admittedly online reviews are a bit of a stacked deck and always should just be a starting point in your real estate hiring decision.
What business person is going to reach out to the absolute worst client they've had in the last 5 years and ask for a review on Yelp or Zillow or whatever site they prefer? And I recognize that no matter how good a person or company is, there's going to be that ONE person that's going to be an issue. I am not a firm believer in 'the customer is ALWAYS right'.
Sometimes the client wants you to do things you can't legally or ethically do, and might just be ticked that you won't do as they say. Let's say we have a difference in our business ethics.
There could be a good reason for a bad review as one person 'in the relationship' is extremely unhappy & wants to be heard. Take some of it with a grain of salt or you can call the agent directly & ask to speak to their current clients. That way you also have the most up to date information.
I'm always willing to share names with new clients.