i pretty certain its volume 13 ( if not then for sure 12) that has the exact last scene of guts screaming in rage as casca is raped.
You wouldn't believe how sick and twisted the plot in the later volumes gets. It kind of makes me wonder if the author if somewhat insane. Let me put it this way, if there's ever more berserks done in ova format, i'm not sure even then, that they'll have the same graphic level as in the manga.
After all when was the last time you watched an ova and seen nude woman, arms tied behind their backs hanging from ceilings with metal collars clamped around their breasts being the only thing suspending them with extra weights tied to their ankles.
"Myau flaps his wings proundly" Phantasy Star 1