I came expecting nothing. Being not a fan of romance, I was at first kinda skeptical because there's a girl on the cover (oh man, I know, I judge books by their cover so much my bad). But I'm certainly surprised, and pleasantly so, as I dived into the story.
I'm aware that it's probably cliche at this point to have romance-driven revenge and undercover Chinese shows are certainly not new. However, I can say that there's 0 romance in terms of development. The show is as simple as it comes (drugs, boss, undercover agent, police, gangs) but it is also neither black nor white in its portrayal of the main characters. You'll fall in love with some you shouldn't be and you'll hate some that you shouldn't be. Personally, I'm very attached to the characters, and knowing them, I fear the ending as soon as I grew attached.
The most important aspect of this show, to me, is the relationship between the two male leads. There're lies, truths, deceptions, covers, and twist and turns that you might never see coming. But through it all, it only melds the two together. Their relationship is more or less build on lies, as expected between a drug leader and an undercover police officer, but it's exactly that that makes the whole story satisfying yet difficult to watch at times.

So if you're looking for some thriller/crime/action without it being entirely romance-driven, or having the main character be pulled astray by a female character, or losing excitement, or lacking 'human' characters, then this show is definitely perfect to add to your watched show collection.

also the male lead is perfectly competent without being naive like some random rookie officers. (MILD SPOILER) Honestly, gwad, no wonder all the drug dealers want him to work for them.

Edit: While the ending does fall a little flat, I'm still very pleased by the drama and the whole ride it took me on. It's not a bad ending, don't get me wrong, it just is flat compared to how amazing the other episodes were.