@Yamibi
Well, that, to an extent, is the whole point.
They're broken. Why are they broken? Because the "civilized" people in authority over them were not civilized at all.
Those in authority claimed that their actions were justified, acceptable. They weren't. They were the actions of evil people.
Based upon what they did, I can't fault him for wanting them dead.
That they are broken people is why they seek to inflict pain prior to killing them; their mental health is very bad, they aren't civilized any longer.
Their desire to inflict as much suffering as possible prior to killing the ones the seek retribution against is clouding their tactical and strategic judgement; pragmatically, they should kill them as soon as they have the opportunity to do so and are still able to escape.
It's stupid to make someone aware that you are their mortal enemy and leave them alive when you plan on killing them in the end; so long as they live, there's the possibility they may successfully turn the tables.
They aren't sane any longer, not as we would consider sane.
It's definitely up in the air if I can stomach reading this manga any further.
I can accept killing the individuals who harmed them, given just what was done, but torture is not something I'm interested in.