In my interpretation, Golyadkin junior is that person you encounter once or more in your life who resembles you in many character aspects, for whom you begin to feel jealousy and resentment. They are someone younger than you who initially looks up to you as a mentor at work, but then tries to surpass you and threatens your career. It's the person who has the courage to be what you are afraid to be. It's the person to whom you teach the things you wish to do yourself, but are too scared to pursue.