As far as physical gore goes i'd probably stick with, Inside. There are definitely gorier movies out there. I have yet to see the entire guinea pig series but the ones i've seen didn't do anything for me but they do boast some disturbing scenes. As far as August Underground, that movie fell completely flat for me. Maybe, it's because i've become so desensitized but i think it has more to do with the poor filmmaking. As a movie there should be some kind of insight into the victims and villains, i received none of that. It just came off as an hour of shock and porn scenes loosely pieced together
Martyrs is definitely a good "sick" movie but there is something about, Inside. The gore felt extremely real to me much like the infamous scene in Irreversible. the most disturbing movies to me have always been the psychological driven ones.
Cannibal Holocaust still remains as the sickest movie i've seen. Yeah, i've more shocking things on the internet than a turtle being split open. The internet has become the snuff beacon for all of us interested in the macabre. However, even though the movie is shit there was something about the turtle scene in, Cannibal Holocaust that just shook me. It could have to do with the age at which i first saw it.