There are some aspects where the series falls flat, but overall it's excellent. For those who don't understand and are leaving reviews complaining about violence... The whole point of this show is showing human desperation and the extremes some people may be willing to go to in order to survive and get through life. It certainly is a challenging watch so if you can't handle blood, violence, oppression without reason, etc, this likely won't be the show for you.
To those who say the show is unrealistic, I would challenge that thought. No one wants to ever believe that they could hurt another person, but the human brain and nature is complex and like many other species, we tend to fight to stay alive. This show relates to both real and fictional stories. For example, a true story of human desperation would be the Uruguayan Air Force Flight 571, where survivors of the plane crash resorted to cannibalism to keep themselves alive. A fictional example could be "The Walking Dead", where people are willing to steal and kill innocents to stay alive. It's gruesome and tragic, but not necessarily untrue. Does that mean everyone will take the most extreme measures they can? No- but it's definitely possible.
The show challenges humans to the point they will go in order to survive (whether that be literally or physical items needed for survival). There are scenes featuring torture, sexual acts, and inhumane living conditions. Without giving away too much, 8th Floor is definitely a villain of the show... But Chun Woo-Hee does an amazing job portraying her. If you liked her performance in "The Atypical Family", you'll likely enjoy her in this series as well.