Peak

Myst, Might, Mayhem
Absolute sword sense
Nano machine
I believe these r all from the same author

Murim Login
Its not exactly similar to this as the mc isn't demonic or anything but probably my favourite murim manhwa, the mc is more funny and silly but hes ruthless when he needs to be and isn't afraid to kill, infact he enjoys killing a lot of the time but its usually a more comedic aspect

I read Myst, Might, Mayhem thanks to you it was really good!