It is hard to isolate the three most important skills for a UX designer; If you are going to a UX agency, you are mainly looking for somebody who can do the job; someone who can design the UX for your product and meet your goals. The hard skills like wireframing and prototyping, research, and visual communication are all essential parts of the UX designer's job. But it would be impossible to succeed with many of the soft skills as well.