What has happened to Creon by the end of Sophocles' Antigone?
At the beginning of the play, Creon appears to be both a successful and benevolent ruler. The fratricidal war between Eteocles and Polynices having ended with both their deaths, Creon's leadership is undisputed. His judgement concerning the burial of the two brothers, although harsh, seems rational in light of circumstances.
When Antigone symbolically attempts to bury Polynices, Creon's harsh punishment of her and refusal to reconsider it in light of the pleas of Haemon and warnings of the prophet Tiresias, bring about the unhappy ending. There are divine signs -- the whirlwind and auspices observed by Tireisias -- that indicate Antigone should not be left to die and that the body should be buried.
By the time Creon finally laments, Antigone is dead. By the end of the play, Creon's son Haemon and his wife Eurydice have killed themselves and Creon has realized that his stubborness has been his downfall; he himself appears to be contemplating suicide as well.