Not exactly universally loved as such but I would highly recommend Fritz Langs "M".

Thriller about a serial killer of children on the loose in Weimar Germany, the police(aside from the main cop investigator) are useless so their only solution is to harrass the criminal and less savory elements of the underclass relentlessly, which makes the criminal gangs decide that their only real recourse is to find the child killer themselves so the cops stop fucking with them constantly.

So you get not just a well executed police procedural, but also a "crime procedural" of sorts where the criminals start paying beggars to act as a surveillance network and similar stuff, alongside the killer himself going about his business and trying to avoid capture by either.

It has some elements of satirizing the rising nazi party at the time, one of the worst of the criminals is deliberately modeled after Goebbels, and the nazi party even tried to sabotage the filming of it because they thought that the original title, "Mörder unter un"(Murderer Among Us) was referencing them, and that the film would be about the nazi party itself.

It also features social commentary over the then existing criminal underworld in Weimar Germany, that tried to portray itself in a similar manner to the Italian Mafia, with codes of honor and as gentlemanly criminals, rather than murderers and thieves. As well as debates over the death penalty and if someone who is insane can be held criminally responsible for their actions.

Its also just interesting on a technical level, its an early sound film so there is no outside musical soundrack provided, only sound that would exist inside of a scene, which makes for a really eerie and moody atmosphere that is utilised in some very impressive ways.