Warning: This article contains SPOILERS for All of Us Are Dead.
All of Us Are Dead’s Na-yeon could have received an interesting arc of dealing with the guilt of her actions and even found redemption had the show not killed off the character so soon. The first impressions left by Na-yeon on the viewers were not good. Always picking on someone, especially Gyeong-su, Na-yeon evolved from just an unlikeable person to a villain when she decided to infect Gyeong-su with the All of Us Are Dead's zombie virus.
What appeared to be a point of no return for the character began to change when Ms. Park ensured that Na-yeon was not hurt by any of the other students or the zombies. The teacher showed compassion towards the student and did not want Na-yeon to destroy her life even after she had committed such a horrible act. Eventually, Ms. Park sacrificed herself to save Na-yeon and showed the student that there could still be a second chance.
All that setup was indicating that Na-yeon would be given an arc about dealing with the traumatic consequences of her decisions and even some sort of redemption seemed to be on the table. The character had even gathered food for her classmates and was ready to risk her life to meet them on the rooftop. However, after having gone missing from several episodes, Na-yeon was quickly killed by All of Us Are Dead's asymptomatic zombie Gwi-nam just before she was going to help her friends. After all the time invested in the character, Na-yeon’s death felt pointless and lazy.
How the group of students would react to Na-yeon's return and whether they would accept her help is a moment that All of Us Are Dead wasted by killing the character. There could also have been a focus on how Na-yeon would continue to deal with the enduring guilt of killing Gyeong-su throughout the end of the season. By killing off Na-yeon right after she had decided to try to make it up for her mistakes, the show also undermined Ms. Park’s sacrifice and made the teacher’s final moments in the series lose all their meaning.
Although All of Us Are Dead had compelling characters and great arcs for most of them, the show did waste potential interesting storylines such as Na-yeon’s. Besides Lee Yoo-Mi's character, the scientist Byeong-chan and the detective Jae-ik could have received more to work with in terms of the story — especially in the latter half of the show. Even still, the moments that Na-yeon was on-screen managed to deliver a good enough conflict for the first few episodes of All of Us Are Dead — the only downside being that it could have lasted much longer.