If you think there are fraudulent reviews going on please contact support with more info. Generally we need to see evidence of fraudulent activity going on (fake accounts, etc.) to take administrative action on ratings/reviews. If it’s just one person who left a bad rating there’s nothing we can confidently do about that since they may just not like the game. If they wrote a review that contains information that suggests that they are giving the rating for a reason other than the content of the game we may be able to disable it.
Thanks