Since you never know who complained and why I still do not trust a review written by someone else. That is just me.
There's no need to trust individual reviews. Look for patterns. Is a broker getting a pile of complaints? Do the complaints sound plausible? Are they all from one country, or are they coming in from various places? Are there threads in Scam Alerts with supporting data?
Another tactic is to flip through the reviews for a broker page by page, starting with the last page - Is the average number of withdrawal complaints per page increasing over time? Prime4x went from some complaints to more complaints to a tidal wave of complaints. The same thing happened with Crown Forex. Yes, a few of those complaints may have been unfounded, but in the end, Omari from Prime stole all remaining client funds and Crown Forex was seized by the Swiss Authorities.