In summary, the Emperor is the one who holds the leash on Darth Vader's power. Despite Vader's immense strength and abilities, he is ultimately subservient to the will of his master, who uses fear and manipulation to control him. The Emperor's ultimate goal is to maintain his own power and dominance over the galaxy, and he sees Vader as a useful tool in achieving this. However, Vader's loyalty and obedience to the Emperor are constantly tested as he struggles with his own inner conflict and desire for power. Ultimately, it is the Emperor who holds the ultimate control over Vader's actions and decisions.