Didnt he do it as revenge for his daughter?
Its a long time, since i read it.
I mean, it was that family that sold the sacrifice and acted like their daughter were kidnapped, instead of beeing sold. Pretending to be like a loving family, meanwhile, villains daughter died in her place.
Maybe? He never seemed particularly caring for her, but I can see him wanting to punish those who went against him. Still not enough of a reason to include THAT tho. Not even out of some "it's too cruel" sentiment, but because it's extremely out of place and perverse, so it immediately takes the story in a probably unwanted direction. This isn't just a cruel sadistic character to me anymore, it's a character who enjoys watching dogs do that to women and who's done it repeatedly apparently. There is a difference in tone and I doubt that the story can actually deal with it.
Saw the update and immediately thought "Oh, the dog rape manga". Sorry, no getting past that and it only seems to get worse. I can hear the people saying "He was always cruel! He was always evil!", yes, but to his own benefit. He manipulated, lied and let people die for his own benefit and pleasure. The author didn't really make clear how this would benefit him, and I don't really want to stick around for a protag who did that for his pleasure. Sorry, but if the author simply wanted to shock the audience, it worked too well.