Well, after having read that Nadia's saga is nearing its end, I have decided to replay the game from the beginning, in order to find out if the problem of the story was the antagonists of the story itself or the protagonist himself and I have come to the conclusion that it is the way in which the same protagonist is written that is bad about the game more than the antagonists.
To give you a specific example during the saga of the Goddess of chaos Eris we can see through the security cameras of the clothing store how Eris manipulates Sarah to get rid of us, so we have plenty of evidence to punish and deny the plans of both without too many problems, but our protagonist does nothing and by the time he finally decides to act Sarah has already blackmailed and humiliated almost all the members of the harem and the worst thing is that we have to see how he does it while our pathetic MC does not do nothing just looking is left be. This situation is the same that occurs with Nadia later on.
In short, Hachi's biggest mistake is not the antagonists themselves, but the way he wrote the personality of the same protagonist throughout the story, mainly his ineptitude, passivity and his poor character development as a leader or strategist, the most irritating already that he always makes the same mistakes and is not capable of winning a battle before it starts.