It's far and in between.
I recommend going to e-hentai and typing in the search filter

male:guro$

That's not guaranteed to find you content that you'll enjoy, but there's sure as hell going to be dead or dismembered guys in there... You can add other tags to narrow down your search.

Women are simply more likely to be depicted in the victim role. There is no equilibrium of content. Other sites that MIGHT help:

https://www.undertow.club
http://sinn4u.blogspot.ro/?zx=ba9c49f7909931af
http://depravityrepository.org/forums/
http://thedarkspot.com
http://www.dolcettish.com