I loved it, but man, every episode felt specifically designed to absolutely crush you at least once.

The new characters in S2 weren't really that impressive, but this season does actually try to give all of them some focus. Chan-young, Tak In-hwan, and Kim Young-hoo already made a good impression last season, and luckily some other new characters from S2 join that list this season.

I ended up really liking Ha-ni (great performance from Chae Won-bin), and I liked her story with Ho-sang. I thought she was a really fun character this season, and made a way stronger impression than in S2. The same applies to Ye-seul, and I'm really happy both survived, so now they can continue fighting over Chan-young (pleasantly surprised he actually survived), and hopefully become friends in the process. I also think I saw Ha-ni teaching neohumans in the end, and I like that idea.

Surprisingly, a lot of new characters actually ended up surviving, though sadly our original S1 characters were not that lucky, with only 4 left alive at the end. I found the story with Yi-kyung and her daughter Yi-su already very compelling last season, and that continues here, all the way to it's ultimately very tragic ending.

Hyun-su has a much bigger role this season. The monster side of him leads to some incredibly fun stuff. His scenes with Eun-yu were oozing with chemistry, and his reunion with Eun-hyuk was an absolute blast to watch. Eun-hyuk's reunion with his sister however went for pure heartbreak. It's disappointing that Eun-yu mostly sits out the big finale (though I'm not sure what she would've done). And as sad as it is, Eun-yu's monsterization process felt inevitable. Go Min-si actually has quite a few emotional scenes this season, but she absolutely nails every single one of them.

The finale: Sang-wook suddenly taking control of his own body to kill Sang-won is a deux ex machine to ensure nobody else has to die, but this was set-up back in the S2 premiere, and I did spend 2 seasons wondering what happened to that loose end, so I am actually glad they brought that back. I'm not sure how Yi-su ends up surviving, but I'm glad she did, so I won't complain.

The ending is very rushed, but I do actually quite like it, even if it really could've used another 15 minutes to properly show it. Living in harmony with neohumans was the only way forward. Neohumans are essentially just evolved humans, just without emotions, but those can be relearned through memories (and teaching from other survivors), so that's just a temporary problem. Yeong-su is back human (or neohuman), and is smiling at an older Yi-su (I actually liked this friendship). Eun-hyuk relearned emotions through memories like Eun-yu told him to, and Hyun-su keeps his promise to Eun-yu to help bring back her emotions, as she's now a neohuman too. There's a temporary "but" there, but it's the start of a happy ending which they so deserve.

I finished watching season three last night. I appreciate that the ending suggests that some normalcy for the survivors is possible. However, I cannot help but feel a little disappointed in this season. One of the reasons why I loved season one was because of the characters. Each of the residents of the Green House apartments felt fully fleshed out. I rooted for them to overcome the monsters within as well as outside. Season two suffered from the introduction of two many characters and several side stories that weren't always as interesting to watch.
Also, while Neo-humans were hinted at as far back as the first season, I feel as if they served no purpose to the overall plot. Even the established rules surrounding monsterazation were thrown out the window and became convoluted in this season.
I loved the reunion scene between Hyun-su and Eun-hyeok and their playful back and forth banter. I was hoping that Eun-hyeok's reunion with Eun-yu would've been more heartwarming and a little less soul crushing. After all that Eun-yu went through this season and the previous season, this decision on the part of the writer's felt a little cheap.

Greatly enjoyed the 3rd season. However....
1) It felt a bit chaotic and hurried at times with character arcs abbreviated, and I was left feeling there were a few episodes short. Perhaps all the CGI expense prompted some higher up to cut things short.
2) The writers seemed loose with their own rules too often. The most obvious was when Sen I Su - the young teen who could turn humans into monsters - got a stab to the chest and we witnessed a dramatic death scene in which she wants to rejoin her mother, Sen I kyeong, in death. We saw many examples when monsters took much worse damage and walked away in easy recovery. And, in particular, we saw a very young I Su take three arrows to the back and get up just fine with an easy recovery with the only effect seeming to be a jump in her aging. We did see many examples of monsters dying through fire, and then Pyeon Sang Uk walks into a massive fire to enable his transfer to his daughter's body only to reappear a few minutes later looking refreshed and ready for more plot twists.
Examples like these indicate the script went into hurried production and perhaps suffered some severe editing. Despite these types of flaws the whole was a fun watch and brought things to a satisfying conclusion.