Of course his plan fails, and Marcus ends up fighting in the arena, under the moniker of Gladiator. In yet another bitch move, Commodus is initially impressed by the Gladiator but ultimately jealous of his popularity with "his" people. The look on his face when he discovers that the Gladiator is none other than Marcus is priceless. He basically wets his jerkin. What a pussy. Infuriated that Marcus has survived, Commodus decides to put himself into the arena against him, in a fight to the death. Oh yes, you are about to die horribly you little bastard, and I can't wait.
Die he does, but not before one final act of little bitchery, before the fight, he visits a bound and shackled Marcus, and shanks him in the hopes that it will tip the fight in his favor and make an easy victim of the Gladiator. Turns out Marcus is just a little bit tougher than Commodus thought though, and there has absolutely never been a more satisfying knife sliding slowly into a throat in cinematic history. Choke on your own blood, Commodus, you miserable little shit!