Name A Drama That Disappointed In The End:
I expected Maru to die and when he didn't that threw me off. The writers made the audience (and myself) feel a myriad of emotions at the thought of losing this character and then bam he's alive! After all he suffered through time and time again you wanted to end the show like that!? Another big issue I had was having not one but two characters contract amnesia at different times. The amnesia arc - though not my favorite- worked in Eun Ki's favor as it helped move the plot along, but Maru's amnesia plot was unnecessary as we were at the end of the drama. It took away precious time that could have gone to seeing our couple finally being happy and at a place of peace.
At least Jae Hee got a happy ending. She finally came to a place of contentment, she had paid for the mistakes of the past and now she was moving forward. The writers did a great job with painting Jae Hee as a anti-hero because she wasn't all bad but not good either. In the end, she was able to redeem herself by spilling everything to the cops and attempting to save Maru's life. Similar to how Charles Darnay of A Tale of Two Cities wasn't a evil person and was able to redeem himself at the end of the novel.
This is not to say that Nice Guy was a horrible show, in fact excluding the ending, it was a pretty good drama. It just suffered from inconsistent writing and a rushed end. And that was the undoing of a otherwise great drama.