What is a reluctant and difficult customer? Is it someone that is conveniently upset? Someone that is not specifically bright?

 No, a difficult consumer is generally someone that did not have their requirements met within your industry. Yes, individuals can be complex. Many people act irrationally, or react to the things in a way that are unfair and upsetting. But behind every single upset individual is someone that wanted something they did not get.

Query for behavioral interview: Discuss about the most difficult external and internal consumer you have had to deal with. What were they difficult? How did you manage them?

Because something is remaining and missing from the consumer, there is no such thing as a truly reluctant consumer. There are only consumers that have a lot of requirements, and so your objective is to respond this query by indicating that you are someone that both tries to figure out what the requirements are and goes out of their way to make certain that those requirements are addressed.

Utilize any opportunity you can to establish empathy with the consumer within your answer, and then elaborate what you have done in the history/past to make certain that consumers walked away much more contented and satisfied. If the end outcome is a obviously satisfied customer for well defined reasons, you will look excellent with the interviewer.