Now going into this, its hard not to draw parallels to The Shield Hero or Tate no Yuusha no Nariagari. MC gets downtrodden, MC gets cathartic revenge against his enemies, goes on to save the world(?), but there is a difference. This manga has a far more malignant streak to it. The description says "heroic" but its far from it. None of the characters in this manga are traditionally heroic. I would even go as far to say that none of them are even "morally gray". It really does make an effort to show the corrupting effect of power and the abuse of freedom when no one questions you and all the characters reflect it. Don't get it twisted, this is a bloody, macabre revenge story with no traditionally good people in it. This manga also does not shy way from adult topics like torture, rape and mass murder.
If you want a more hardcore take on Tate no Yuusha no Nariagari, this manga can scratch that particular kind of itch very well. For those who don't have the stomach for these kinda themes, its best you stay away from it.