imma try recommend manga nobody mentionned:
im kinda surprised nobody mentionned: 1.
Region which is like from the same author as
BM: Nectar (BioMeat: Necter)
theres like 2.
Mahou Shoujo of the End or 3.
Mouryou no Yurikago or 4.
Kyonyuu Dragon that look a bit like
highschool of the deador like: 5.
Ibara no Ou where ppl get eaten by monster (gruesome) and stuff
I liked 6.
Enma too (its a oneshot...kinda fun to read =3)
7.
Satanister a fight between assassin and their victims...more or less an horror...still gruesome
8.
Dark Metro is kinda fked up too...you can read it if you got the guts to...hah...
9.
Mushi to Medama to Teddy Bear is fked up in its own way...like killing with a spoon...omg...but like less bloody just so fked up still...lol...