I felt i had to write this because it feels like the other user didn't even read half of the first chapter before writing a review.
Pretty much everything they say they wish the author had done actually happens. In the first few chapters.
Dark classes are hated and the dark mage is also ridiculed because it is the weakest dark class. The MC's family is a family of holy knights and has a particular hate for the dark classes, i guess they see it as a stain on the family honor, that's why the MC's father plans to kill him.
The only ones focused on the black mage being weak are his party members... and to be fair it makes sense for them to care about the class performance since they fight together.
Oh and i'm not trying to defend the plot. It's terrible. Saying that the dark mage is weak is unnecessary to the plot, but the author said it... and then it is shown as a pretty OP class from the beginning. The class doesn't have skills but you can learn any black magic spell, which seems flexible, and right in the first fight the MC binds the demon king with a spell, so he is obviously useful to the party. After reaching max level he can also summon demons that are on par with holy knights. This just seems like a plainly strong class to me.
It may be because of the max level... except the MC got to max level in 5 years, i doubt nobody ever got to max level as a dark mage. Oh and the whole concept of levels is stupid because a level 1 hero somehow is unskilled, but strong enough to be dangerous for a level 999... it doesn't make any sense.
The idea to tell someone he regressed seems like a nice change, but then he goes on and also tells this info to the demon king. Why???? It goes well, but he had no reason to risk that. Also before the regression the fiancee was imprisoned because they needed a saint for a barrier... but the hero party has a saint. Since the fiancee was a pretty powerful noble, doesn't it make more sense to imprison the guy that later got into the hero party and put the fiancee into the party?
It's just terrible.