8/10. This is a story about child soldiers, which is some heavy stuff. Kill the Dragon is more thematically dense than your average manhwa fare. Themes include child abuse, drug abuse, PTSD in every form, duty, sacrifice, camaraderie, etc. etc. - it's a war story, it has war story themes.
The hero is underpowered and remains underpowered. He closes the gap between himself and his more talented peers with a strategic mind and excellent leadership skills.
There's character development aplenty, in both positive and negative directions in response to the grim environment of the story's setting which asks that the military cultivate children into emotionless weapons of war to fight a losing battle against an inexorable alien enemy.
The setting is not the most creative or inventive but it's perfectly functional and doesn't want or try to be the centerpiece of the story.
The supporting cast is expansive and material - all the characters have some degree of emotional depth and internal conflict. There are no good and emotionally healthy characters in this story. Everyone is dealing with demons.
The art is not for everyone but I enjoy the slight variation from standard manhwa style.
Lastly I want to mention a really heartbreaking moment for me late in the story when
the hero helps a terminally ill young woman abandon her military post so she can spend the remaining few months of her life with her lover. He helps her escape from a military compound in exchange for information she has on the top brass, but when he later opens the drive she gave him, he discovers only an apology from her instead. Rather than recognize that someone close to him manipulated him out of emotional desperation, he starts searching for hidden clues in the apology because he has to believe that his exploitation is meaningful, that his suffering is meaningful, that there's rationality behind every decision by which others betray him. Or else how can he cope with the cruelty he's been victim to as a child soldier?