There's a rule when it comes to handling complaints and bad reviews on social media. The same rule applies for compliments and good reviews, but those are easy. Handling the complaints can be challenging and you may not want to do it, but as a rule you must reply to everyone who is talking to you publicly whether it's good or bad.
This is an absolute rule. There are a couple of extreme situations when you don't reply, but they are so rare that I hesitate to mention them for fear that it could downplay the message that you should reply to everyone.
There's another rule that is unfortunately getting broken just about every day by many social media and reputation management companies. Canned responses should never be used. Every response should be personal, written by an actual human and not repeated. It's better to make a short, sincere response than anything that came out of an automated system. People can tell. You will never appear more insincere as a company than when you reply to someone talking to you on social media with a form letter.
In this infographic by Pardot, we have a chance to take a look at five of the most prominent "complainer types" on social media. If you can identify the category that a complainer falls into, you'll have a better opportunity to handle it appropriated. One does not have to be a psychologist to understand personality types. You just have to open your eyes and ears before opening your mouth.