Since you said "career" specifically, I would say communication. If you can tactfully ask and figure out what direction you need to develop in, or if you can be

Since you said "career" specifically, I would say communication. If you can tactfully ask and figure out what direction you need to develop in, or if you can be persuasive and make a compelling argument, your can be much more effective in advancing your career. You'll also make friends and allies along the way.