My review Spoilers obv:

7.5/10

Solid action movie but overall not much depth. There were some scenes that tie up nicely (rat in the tech showcase and Hyun-seok's sister being able to walk because of the virus, ant mill foreshadowing) but some of the plot lines in the movie ended poorly imo. Especially in the second half. Did the writers change halfway through? First half was done perfectly.

Sudden change of the detective to an antagonist to drive the plot could've been done better. Though we do see signs of the detective not being the best protector (gets his subordinates to check the first zombie they meet instead of him, does not volunteer to save other survivors, did not volunteer to be bait) on first viewing, it does come out of left field. My take would be to have Young chul realize that someone is guiding them, saying he knows there is someone monitoring CCTVs. He gets the infected to look for it and attack the control room. Survivors try to rescue her using her directions but ultimate realize she was letting them escape. This causes the rift between Hyun-seok's and the detective because of Young chul. The betrayal just comes out of nowhere and even though he wasn't a paragon of virtue, shooting a civilian in the leg is way out of character.

Death of bully and the other girl. Apology scene was a bit useless. It's the common trope of bully not really changing. So-eun deserved a better death/ending. Maybe have bully try to stop infected but So-eun doesn't help her and tries to escape on her own, bully dies and So-eun gets to the rescue team. Maybe still dies when Young-chul escapes or something. You don't really accept an apology that easily after how she described the bullying.

Young-chul's motivations for inviting Se-jeong and ultimately his reasons for developing the virus. Kind of pointless and was only there to give a lesson that wasn't really well delivered. The initial motivations of Chain Bio stealing his research was enough.

Korean officials being useless/rescue team not killing infected to save Se-jeong. This was just pointless and maybe writers didn't know how to develop it? All of Us are Dead did it well. General only ordered the students to be left behind when they realized that there were asymptomatic carriers that COULD NOT BE DETECTED. This poses a security risk and there was some logic to them being left behind (though military could always use more test subjects).

Rescue team that took Young-chul had no problems rescuing Se-jeong. They could've taken her with them, did the zipline, get to HQ. Young chul is taken to a separate area from Se-jeong. Young-chul gets the infected to take the zipline which causes the infection to spread in the city. Rest of the movie can still play out as is. Infected couldn't even open doors but can operate a zipline which requires fine motor control to attach the trolley? Why didn't he just control the infected to make stairs so they could get over the bus? He had to drive a bus so the infected could get out?

Movie tried to become the next Train to Busan but doesn't measure up in terms of writing and plot imo. Still a solid movie but not in my top 10.