Monster is undoubtedly the most visually striking anime I have ever watched. But before starting, it is essential to mention that I am a very picky watcher and find pleasure in the scrutinization of shows and movies, finding plot holes and other theories. However, it was surprising as I was unable to scrutinize the show at all. The author has taken in a considerable amount of plot holes into consideration, and hence was born this impeccable story.
I fell in love with the show in the first 20-30 episodes. It was as if I was a piece of metal in the same room as the biggest magnet in the world. The suspense, the characters, and most importantly, the progression of events were truly delightful to watch.
Although, as the anime progressed, I found myself rewatching certain episodes, as I had trouble remembering the characters. This is not to say the show was boring, but it was quite complex for an anime, and I for one found that extremely alluring. The string of episodes where the author takes time to explore individual characters and their past, ultimately leading to the boldest endings is truly the cherry on top, and you will appreciate it once you have finished watching the anime.
The 7th segment of the anime is the best, in my opinion, as it acts as a sort of converging point for all the characters' past to meet at one particular point, and it all starts to make sense, sort of like solving a difficult math equation and feeling like the answer was staring you in the face.
Overall, it would be an understatement to call Monster a masterpiece. Please watch it if you are a fan of psychological thrillers and criminal novels. Definitely the best anime I have ever watched.