This season was a step up from season 2, but still nowhere near as good as the first season.
I did enjoy this season for what it was, even if the final few minutes were rushed and didn't fully explain what needed to be about neohumans and what happens to the main trio.
I do have some issues overall. Mainly, the plot. Season 2 built up so many random characters and plot points, seemingly for nothing because almost all of the new characters introduced were killed off and plot points disappeared.
Maybe I'm just dumb, but I guess I didn't fully understand Lee Jinwook's character and what he wanted. I thought that he wanted to find more special infectees, but then he killed all of them. So what was the point of him as the main villain? This leads me to my second main issue, which is lack of payoff. I think we all expected Hyunsu and Jinwook's character to have an epic final showdown, but we were denied that. The whole ending battle was lackluster. Not only that, but I thought that Hyunsu's ability to turn monsters back into humans was leading up to him kicking Jinwook from Yisu's head, but he spent all of a minute in there. It's weird. We're told that Hyunsu is special and we kinda see that, but not really. Really frustrating for someone who is suppose to be the main character.
Okay, so all of that to say, I did enjoy the first half of the season. It was fun to see the main trio back together (even if, as much as I loved having him back, bringing Lee Eunhyeok back didn't serve much purpose). I also really enjoyed Monster!Hyunsu. He was a fun change and the scene where he and Human!Hyunsu talk and become one was well filmed and cool, but perhaps should've bee longer and more built up.
Ultimately, both this season and 2 don't hold a candle to the first season, which had a focused plot, good character arcs, and more importantly HEART.