I have not read this myself, but have seen comments - have you tried Assassination Classroom?
Oh, and for ones with a lot of blood, Bleach (lots of fights - no real assassinations)and Vassalord (vampire manga - but pretty sexy though) and then there is Gantz (I could not carry on with that one - it was kind of disturbing)
Dogs.
I actually have read Assassination Classroom and very up to date with it but it's more of a commedy than blood and gore
Warning, list below might be a little hardcore blood and gore..but still fun to read (●'◡'●)ﾉ
Try:
Tenkuu shinpan
7 seeds
kingdom
Rainbow
Aphorism
Deadman Wonderland
Apocalypse no Toride
This is about a group of students who decide to play a 'game'... Between them is supposed to be a traitor, the fox. This makes them a little crazy and so, murders take place.
http://www.mangago.zone/read-manga/shuuen_no_shiori/
Manhole
Manga with a lot blood and killing with muders and assassins =D I just finished reading Trash. so I'm looking for manga like it <3
Thanks in advance! (๑•ㅂ•)و✧