The premise could be interesting, but if I may criticize a little bit, I'm honestly thoroughly confused by the writing.

One paragraph, she's breathing hard from broken ribs, the next, he looks at her "lifeless body", the next, she's just unconscious and breathes better, the next, she's convulsing … What the hell is happening ?

Also you mix present tense in the middle for no reason.

At the start, she's just an anonymous victim. But at the end, it's almost as if he knows her.
At the start there is a crowd, and after the fight starts, it's like they're alone in an empty room.

Also you mention a referee, but he then completely disappears. Why doesn't he stop Marcus, or at least try ? What are the rules of this fight ?
I like that at the start it looks like a standard if unbalanced fight. But it would help the story to talk about the context of the universe along the way and explain what's happening in that room.
Otherwise, it's just a big burly guy raping a little girl for no reason, and that doesn't make for a very interesting story.

And as I said, it needs a huge load of coherence. Right now, it seems like completely independent paragraphs loosely based on the same theme, put together in a slightly random order.