I'm looking for a serious manga with a ruthless protagonist (can be male or female.)
By ruthless I mean somebody who accomplishes their goal by any means necessary. In a situation where the mission is to retrieve an object but an ally is injured, the protagonist would abandon the ally than risk the mission. Someone who has no misgivings about using innocent bystanders as meat shields.

The epitome of a ruthless protagonist would be Guts from Berserk. Some famous manga with ruthless characters I've read are: Afro Samurai, Black Lagoon, Golgo 13, Kozure Ookami, Vinland Saga, Eden: It's an Endless World!, and Death Note.

I'm looking for hidden jewels like Shut Hell and Wolfsmund.

Code Geass anime.

i dont need help finding anime. thanks. its flattering that you think i havent watched code geass.

You should practice manners when asking for something.

Onani Master Kurosawa

Kami no Kodomo

You've already read everything I was going to suggest, but it sounds like this catagory could help.