I had been curious of how the story would unfold. There were some really interesting characters, but the MC had been annoying from the start. It's his second life and he's still going around like a dumbass.
In order to let this guy win, all others had to be dumbed down as well.
Spoiler:
He knew the King was going to die. It was obvious that it was the empire. Preventing his death would have not kicked off the civil war in the first place. He didn't even bother asking the Duke to look out for the king. Not to mention, why would an assassination have to take place on the same exact date? Did his health restoring bracelet not have any impact on it? He banked the outcome of an entire war on it.
Waltermine was a decent character, and he's supposed to be smart. What reason did he have to recruit a small baron who's an enemy of a friend? Could have just hired spies to steal the crossbow.
MC already knows who the spies are, didn't bother to do anything about any of them. Instead went on war after war and killed every strong person of their kingdom. Why not just cause some trouble in the empire instead?
The Duke being negligent, the king being a slob, and MC being oblivious, every other noble just being greedy. At this point, they deserve to get taken over by the empire. The crossbows or the bombs, even MC's aura, anything slightly decent is all from the empire anyway, and even the people looked happy there. Even after a second chance, this kingdom is still garbage. Might as well surrender.
MC abusing slaves is kind of nasty too. For the 20 years they are supposed to be working, they haven't recieved any compensation so far. And he could afford to hire more workers or could have tried for some automation, but chose to grind them to their bones. The worst part in the beginning was destroying the dam gates saying "we'll build again" just for a show.
Crappy, stupid, oblivious, conceited, greedy and honor less behaviour from MC has been very consistent.
Other characters are mostly nice. His father is another person with head in clouds. What happened to all that honor and stuff he spoke about? He's okay with all this if it's beneficial.