This question is layered and can be interpreted in many ways. How you will interpret this question will give your interviewer insight into your outlook on the world. Not only is the interviewer trying to get an idea of who you are, but also an idea of your communication skills. It will also inform them of what you perceive as a difficult person. They're keeping a keen eye out for any 'red flags.' In the simplest terms, in this scenario, the last thing you want is to plant the seed that the difficult person in this scenario was you.

When relaying your example of a difficult person, pay close attention to the nuance of this question. It doesn't suggest a personal problem between you and the difficult person but wants to know your interaction with the situation, and how you communicated with them. Objectify the situation, exhibiting an emotionally mature perspective, and how you navigated this terrain, ultimately leading to a successful resolution. Avoid assigning blame. You don't want to come across as part of the reason you and this difficult person didn't get along. Focus on the positives, and how the overall outcome benefitted the team. You want to come across as a people person with enhanced communication skills. This question is meant to assist in evaluating your non-defensive communication skills, your aptitude for diplomacy, de-escalation, and negotiation. Take care to exemplify this mentality.