Line Walker (2014)

Both feature smart and badass FL who is a undercover cop, morally grey ML.
The way both leads manipulate each other and fall in love for each other is similar too.
Similar plot twists regarding the leads.
LW has a bit more plot on other uc cops tho.

Raymond Lam the ML is the lead actor in both dramas and he plays a cop. Both have action and are crime dramas.

Line walker has more comedy, but both dramas are just as intense and action-packed. If you like spy dramas, with interesting characters and have great pacing/storyline. I recommend both of these dramas. Michael Miu is amazing in both.