Responses
Try https://www.mangago.me/read-manga/from_the_red_fog/ he is pretty heartless though but omg give it a try it's amazing you can also try https://www.mangago.me/read-manga/pumpkin_night/ or https://www.mangago.me/read-manga/brutal_satsujin_kansatsukan_no_kokuhaku/ (but this one he kills the ones who wrong others like he would kill a man who r@ped girls, killed babies, in the most BRUTAL WAYS so he definitely isn't heartless to purely nice people.
Recommend some mc who is anti hero, doesnt hesitate to kill those who wrong him, but not that heartless like FFF Class Hero