If you describe someone as unfulfilled, you mean that they feel dissatisfied with life or with what they have done. You must let go of the idea that to be single is to be unhappy and unfulfilled fulfilled
If you use unfulfilled to describe something such as a promise, ambition, or need, you mean that what was promised, hoped for, or needed has not happened. angry at unfulfilled promises of jobs and decent housing The election had raised hopes that remain unfulfilled. fulfilled