Anakin is destined to 'Bring balance to the Force' by some old mysterious prophecy. This prophecy is a bit vague and there could be different interpretations. Most people automatically assume that 'balance' means that he will kill off Jedi until there are equal numbers of Jedi and Sith (Yoda + Ben vs Emperor + Vader) or that he will do something to cause the Light side and Dark side of the Force to hold equal power in the Galaxy. I think there is a different way to interpret the prophecy: Anakin Skywalker fulfills the prophecy of 'Bringing balance to the Force' by creating Luke Skywalker. Notice that the Jedi are a very unemotional, controlled, logical, and unattached order, as AotC showed us. They are almost inhuman in how they emotionally react. The Sith are on the opposite extreme. The Sith are fierce and full of hatred and love, very extreme emotions. By creating Luke Skywalker, Anakin brings Balance. Luke Skywalker, at the end of ROTJ, is the last remaining Jedi. He is also very different from the Sith and from the old Jedi. He is emotionally attached to Leia and Han and loves them, while the old Jedi could not. He's also let go of his hate that he once held for Vader. Luke is capable of anger, as we saw in his duel with Vader in ROTJ, but he's also capable of keeping his anger from driving him out of control. Luke is right between the Jedi and the Sith. He's really more neutral than pure lightside Jedi. Vader's actions fulfilled his destiny at his last moments of life. He saved Luke and destroyed the Emperor, leaving a just one single balanced 'Jedi' in the Galaxy. Luke represents balance. Anakin brought him. So he brought balance!