Types of killer review
For hotels: noise and cleanliness (guests will put up with almost anything but 'being kept awake all night by....[traffic/nightclub/clanking lift]), written by a frequent reviewer (especially in the case of sites like TripAdvisor and Yelp); for estate agents: lack of communication, staff attitudes. But there is an easy litmus test for any business owner or manager: it's the review that keeps you awake at night, the review that you dread a guest or client reading.
Strategies for managing killer reviews
The first thing, providing the site in question allows, is to respond (we are consistently amazed that businesses that don't). Apologise (even if you don't feel an apology is warranted - remember to keep the potential customer in mind), and explain why there will be no repetition of the event. Don't punch back, however tempting it may be.
If your website has a link to a site containing a killer review, seriously consider dropping it until you are sure it's not damaging your business.
And last but not least: get Dialogue working flat out so potential customers don't feel the need to go elsewhere for credible reviews.
Note: Whilst linking to external sites might seem like a 'great idea at the time' statistics consistently show that only a small proportion of visitors will return to your site afterwards.