I dont understand the story anymore. Where did the plot of his little sister go? That annoying filler that just prevented the MC from seeing his kids growing up.
The old man is weak politically. Its why he is E-ranked and I bet its due to people like that elf and the punk ass kid. Just because he didnt retaliate back then doesnt mean he wont in the future.
You forgot one important thing.
CONTROL.
People will want to dispose of powerful superweapons not in their control while keeping some for themselves. As the MC is a hero that the fantasy isekai leaders can't control, they chose to kill him.
They got riled up because the childhood friend is a polarizing individual and her first impression is very bad.
Also you have to add that any person who harbors dark ambitions would be able to subvert their country/state/kingdom or empire really easily that they wouldn't be executed.
The...
Which is ironic because those same actions also create more enemies like those terrorist.
In the fantasy world, antagonizing the person who saved you would likely be the seed for a revolution or another type of demon lord.
We are not even sure if its the demons who started that fight. It might...