Do not forget that alliteration is a sound mechanism, in which the same initial consonant sound is repeated several times within a line or phrase. It is a poetic device. When used in prose the purpose is most often to make a line more memorable, or have a greater impact.
Keeping that in mind, it is best if you are reading an early translation rather than a modern translation of the play. You will likely find several examples of alliteration in one of Creon's speeches. As the king in this play, he is the most flamboyant speaker because he wishes to sound wise, confident, and powerful. He does not speak plainly because he wants to be taken seriously.
One famous line of alliteration in Antigone comes in Scene 2, when Creon first brings Antigone in to convict her in front of his people. At this point of the story, Antigone is clearly guilty, and now her sister Ismene's part is questioned:
Go, some of you, arrest Ismene. I accuse her equally. Bring her: you will find her sniffling in the house there. Her mind's a traitor: crimes kept in the dark cry for light, but how much worse than this is brazen boasting of barefaced anarchy!
Not only does the alliteration in the final line bring home his point with demand and finality, but his diction as well.