TLDR: A fantastic drama that is worth the watch!

Overall, extremely impressed with the show. It's certainly one of, if not the most, well-written serial killer mystery k-drama I've had the pleasure of watching. Unlike most other dramas that reveal the killer relatively early on (with the latter half just focused on finding evidence / catching said killer), this drama continuously keeps you guessing–every character is a potential suspect, and no one is free from suspicion until you learn the Eraser's true identity the very last episode.

The story was also incredibly compelling. Dong Baek's powers are badass, and the ways it's used is so cool. It's also been a while since I genuinely felt so bad for a character–Dong Baek's past (death of his mother, guilt from the death of his best friend), coupled with the burden he has to carry from all the memories of crimes, really struck me. He's just a poor soul :(

Admittedly, the drama does become messy with all the twists and turns it tries to plot. There's a huge ensemble of characters, which makes it sometimes difficult to follow. The show sometimes feels like it's just revealing pieces of information one by one instead of allowing you to figure it out yourself, as a mystery drama should (SPOILER: for example, there are no hints about Dong Baek's past / the existence of his sister until the very last episode, beyond the fact that the Eraser has similar powers).

Some plot points are also retrospectively strange given the final reveal. For one, what was the point of the Eraser sending a painting of the angel with the claw hammer to the cult leader, if it was just to taunt her own brother? Or of the two women in plaster casts, to taunt Sun Mi? (Or maybe I'm just missing something....)

Acting-wise, Yoo Seung Ho and Lee Se Young did an absolutely fantastic job with their roles. Yoo Seung Ho is probably born for these hard, badass detective roles tbh, and Lee Se Young kills it as a takes-no-bullshit officer. The Avengers team (the two main + the two sidekick police officers) make an absolutely adorable team. I was pleasantly surprised that there was no romance between the two main leads. Not to say the leads didn't have chemistry (they did–a lot), but it was incredibly refreshing to see a drama where the leads just work in a professional capacity.

Not too many sung OSTs, but the instrumentals were all great! A lot more than I thought there were, and gave the drama a great ambiance. Would recommend a listen to OST: Sad Song.