Why does Odysseus kill Antinous first?

Odysseus kills Antinous first because he was the suitor's leader, both morally and politically. Antinous was the richest, loudest, most obnoxious, and most ungrateful of the suitors. He abused Odysseus by throwing insults and then later a chair at him. Further, Antinous doesn't suspect a thing, and Odysseus must eventually kill them all anyways.