What most makes Creon a villain in this story is placing revenge above sacred duty.
The text focuses on the importance of burial as a principle, as a sign of respect for human dignity: "to bury the dead was a most sacred duty." Several lines are dedicated the description of this practice, as a way to emphasize how outrageous it is for Creon to refuse it, going as far as to make it "a crime." He basically made his revenge against his enemies ("those who had fought against the city" like Polyneices) more important than the sacred funeral duty by banning the burial of these enemies.