Anakin fulfilled the prophecy before his redemption arc, because he took two Sith and hundreds of Jedi and made it 2 Sith and two Jedi, therefore it was balanced
I SAVED THE ENTIRE GALAXY AND MY SON FROM PALPATINE DESPITE BEING DARTH VADER AND BEING UNDER HIS CONTROL. I STILL AM THE CHOSEN ONE AFTER ALL. THEN PALPATINE CAME BACK TO LIFE IN THE SEQUELS AND YOUR REDEMPTION WAS ALL FOR NOTHING, RIGHT? OH……; (SNIFF!…….)