This is a very hard question to answer for every other interviewer because each of them have different expectations in a candidate.
1. Self Confidence – Candidates must be sure of what they are doing, and to show this one must answer questions articulately while stating facts as they are. This will involve saying no to something you do not know. A candidate with low self confidence will run into situations where he won’t take risks or make “the tough calls” just because he is afraid of being wrong.
HR will always be willing to compromise on some of the other attributes as long as they feel the person in front of them will be able to fill the gaps by investing his time and efforts, but if someone is not truthful then they won’t be able to trust him or his work.
Lastly, and to make sure you have the whole picture, there are always extra-points for technical knowledge in the field in question, and this may even be a requisite if they are looking for an expert in a specific field but most of the times this is one of the attributes with less weight in any interviews.