Serial killer drama/movies

Any good drama/movies where detectives chase serial killer, with lot of intensity and feel where you suspect everyone lol. :D
Thanks everyone who can help :)

I'll second Siren, even though it's not so much about "whodunnit" as it is the tense cat-and-mouse game between the killer and one of the detectives, with his partner/lover at times being used against him as a pawn.

I also liked Ishi no Mayu.

Thank you all for your answers,  i am really short on drama's so this is great help! 

Yea IWGP is great i like it a lot, ishi no mayu is good two, for now i think to try  The Chaser or  Siren

Gap Dong

"Love me if you dare" is a drama where the guy chases serial killers and you hardly know who is the culprit until he unfolds everything.

white christmas , a master piece , i don't want to spoil it but  there is no detective  but definitely a   killer ,everyone suspect everyone 
bad guys  "criminals helping a detective to  chase other  criminals"  one of the best dramas ever 

 hello monster      not sure if it's what u r looking for but check it    one of the best this year 

White Christmas - Watching it right now and I already suspected multiple characters XD It hasn't a real detective, although people want to find the murderer at the beginning. Idk if this is a spoiler but after that it's more like a game between the killer and the "victimts".

Also Bad Guys - It has both detectives and serial killers. Althogh the identity of the serial killer is known at the beginning, soon you'll find yourself questioning if he's really the killer and start suspecting others too.

Both are highly reccommended :)