Here's an example of very degrading sex that's not rape play either. (The domme gives orders to the sub, and there's one act the sub is reluctant to perform, but throughout the scene the sub expresses consent verbally and physically.) This story is extremely gross porn; there are two characters; the domme is a crossdressing woman; the sub is a woman; seriously I mean the "gross" part, you have been warned: Piggy, by Jen Cross.

I didn't read the story based on your warning and the fact that you gave a ... synopsis ... that seemed sufficient.

I think I see your point; it does seem possible that sex could independently be violent and degrading, for most values of "violent" and "degrading", without utilizing rape play, although that would seem to be the easiest route.

It might be fair to classify all reluctance play as "simulating something close to rape" (e.g. "Stop hitting me"), and even anything involving restraints if you're being very inclusive

That's basically what I was thinking of.

if someone's begging to be hurt and to do something degrading (and there's no roleplay where they're being forced to or anything)

Funny thing, but I seems to have been thinking that "degrading" meant nonconsensual. Which is stupid, now that I think of it. I guess "degrading" is an ambiguous term, come to think.