Psychological thriller
Possibility of Main lead being the killer
Doesn't hold back in terms of gore
Dark theme/colors
Main lead is a cop/detective
Killer has a particular M.O.

It has that Bubbly Female lead and Serious Male Lead trope.
Takes place in hospital.
Supportive and not-bitchy co workers.
Light hearted.
Female lead takes the first initiative.

Personally one of my all time favorites. Its not dark has good morales. And a bonus of really good poems.