So the tags on this drama are thriller, mystery, psychological, romance, crime, and melodrama. I may be biased, but I believe that this is one of the very few dramas that delivers on all tags and does it so well. It's hard when dramas try to do so much at once because then it veers off into one genre more than the other OR may feel offputting; however, Flower of Evil is unique. The crime, mystery, and thriller aspect of the drama was so well written that it kept me on my toes throughout the show. These three tags were the bulk of this drama, as we can tell from the synopsis and images. The writers bring in the psychological aspect that acts as the backbone for the characters. It's important to highlight that the romance didn't take away from the plot. Instead, it added a lot more to the characters' depth. Then the melodrama part just ties it together, creating that anguish of emotions.

The foreshadowing, symbolism, and themes were greatly weaved into the story. For example (spoiler), my favorite symbolic moment was when Do Hyun So and Cha Ji Won were standing hand in hand to meet Detective Choi. They both were wearing black. Do Hyun So in all black and Cha Ji Won in all black except her inner white shirt. However, the all-black Do Hyun So represented "evil" and all the things against the law. Cha Ji Won in black because she was supporting Hyun So and even helped him. However, her white shirt represented her strong sense of justice as an upholding law-abiding officer.

I appreciated this drama because the primary investigations were all correlated/connected into a bigger scheme. Example 1: A character made an appearance again later due to the results they closed from a prior case. Because of his second appearance, it leads to the investigation hotter to the potato. Can we just appreciate the thought that went into this?

ACTING/CAST/CHARACTER
So I'm Lee Jun Ki biased because he's a good crier. His roles that he takes on has always been quite similar, in my opinion. However, he does them so well, so I can't even complain. Do Hyun So is one of the better-written anti-heroes and has one of the best character developments I have seen in a while (probably because I'm only in rom-com land). He's always between this line of good and evil. You feel bad for him as you know his past, but you're not sure how evil his character may be due to how much we know about him.

Moon Chae Won as Cha Ji Won was such a great pick. I haven't seen Moon Chae Won's works in a while. She has surely improved as Cha Ji Won. I don't think her presence in the drama did not fall short of Lee Jun Ki as Do Hyun So. A strong female lead that was not a damsel in distress at all! She did the butt-kicking so many times for her husband. Her strength as a mom and a person was so well portrayed. She wasn't invincible, as we still see her inner turmoil as she struggled to do what was right and deal with her husband's deception.

All the other characters fulfilled their roles really well and came off as convincing. For example, even the mom, who was not well-liked, struggled in doing what was right vs. wrong.

NEGATIVE (spoilers, proceed with caution)
While I loved everything else, there were still aspects that I disliked, which is pretty much the latter half of the show.

The awkward product placement scene at the station where they offered those little pouch drinks. It felt so awkward and threw off the whole scene for me.

Do Hyun So's sudden emotional overflow. While I understand it was a reveal of him realizing his feelings, it felt abrupt. Especially if I keep in mind that he has an anti-social personality disorder. Which he has had for his whole life, without proper treatment. I mean, I'm not claiming to be an expert, but I feel like it should've been slowly peeled to us. Again, personal opinion on this part. I think it's because we see such a stone-faced, manipulative, and evil character that it feels weird when it all of a sudden turned off like a light switch.

We waited for the antagonist forever. The whole show was built up for the big reveal. When we actually got to see the scenes from the past, the antagonist felt quite lackluster compared to Do Hyun So's dad. It made me question how this person was supposed to be our antagonist in the first place. When I saw his performance, he was seen as sloppy, and the setup felt really convenient for the antagonist to do what he wanted. I feel like I wanted to, I can justify this as this was the sole reason why he failed in the first place. But still, have to admit that I felt pretty disappointed.

Ending/the last episode seemed like lazy writing to me. I felt like the writer wanted a decent way to justify Hyun So as a manipulative and not mentally sound character, along with his ugly past. Instead of working something out for Hyun So for how he is, they decided to do away with everything but not his emotions, AKA making us sympathize with him. This was still done acceptably, especially within just one episode. We still see Hyun So's character development and relationship development with everyone around him. He does get the closure that he finally needed, even though it didn't give some viewers the proper satisfaction. I just feel like there could have been a better way of justifying Do Hyun So.