Fiction crime undercover books

I am looking for specific books in which a cop or detective goes undercover, maybe to stop a drug lord or something similar. I do not want cosy mysteries. I am leaning more towards psychological crime thrillers. I'd like it to be set after the year 2000, so no historical or period pieces, please. Geography isn't too important, but bonus points if it's not set in the U.S.

Any suggestions are much appreciated.