I think it's much more probable that he will hang himself or get shanked. Prison's are practically eco-systems unto themselves. It's not that uncommon for brutal smaller prisoners to develop positions of power in prisons, however those that are able to do so would possess far more street smarts than war machine imo.
We have no idea what will happen to him in there, but i'd be interested to find out.
If War Machine DOES end up getting raped in prison, then no doubt it will be some type of gang style justice where prisoners in a position of power want to make an example of him...... who knows, maybe Big Bubba connected prison guy had a soft spot for Chrissy Mack and wants revenge lol.
Prison is a terrible place, many predators on the outside find themselves prey on the inside. War Machine can defend himself, but prison is far from fair and if he makes powerful enemies (he's a dumb cunt, I could see him doing this) and they feel like he is a risk to take on 1 on 1 then they will do whatever it takes to mitigate that risk, whether it's numbers, weapons etc etc.
I remember reading a true story several years ago of an inmate (big guy, like 6 foot 3) who had refused another inmate a packet of chips or something we on the outside would see as completely inconsequential. Months later, the other inmate (smaller, but equally as brutal in this instance) shanked him from behind then raped him while he lay dying, bleeding to death.
I struggle to think of a worse way to go out than that. Prison is a horrible place but based on what I've read War Machine belongs there. Consider Steel Libido ingredients before you start using them.
With regards to him being the alpha predator in prison due to his mma background, some people are talking about him like he's Fedor or something, remember this is the same guy that got plebbed out by Yoshiyuki Yoshida in like a minute. There are lots of big, brutal people in prison, even in a 1 vs 1 situation i'm sure every prison would contain sets of prisoners who would crush War Machine in a fair fight... and fights in prison are rarely fair.
Brazilians. We had a few stories of pro fighters vs. the same kind of thugs you would find in a prison system using the same tactics. As I recall none ended in submission or scorecard and BJM wasn't there to pull the offending gang members off them. This is the real world not the Marvel Universe. Getting jumped or having a guy the size of Brett Rogers unpredictably attacking you is not the same as fighting in a weight class. Prison isn't chasing down a purse snatcher or dog abuser and being in total control. It's unpredictable and scary and you can be facing groups of men who work in packs. Doesn't matter if you're a bear or a lion the wolves will find a way to get you if you cross them.
This is the same line of thinking someone who owns a fighting bred dog thinks. Does not matter if your dog is a champion who tore up other big scary fighting dogs in a controlled regulated prize fighting environment.. you can't illogically think he can kill wild animals especially pack or hungry ambush predators. That kind of ignorance gets displayed and then your left wondering how 3 pathetic coyotes wandered into your backyard and ate him because you thought "blah blah my dog is tough ain't no coyotes gonna fuck with him he a fighting dog" well it's not the same thing and if they're hungry enough they will find away. Even worse when it's wolves who have 40lbs on that 65lb dog....That's how prison is it's not sport and the rules aren't the same, entirely different animal with a different agenda.