In aspiring to behave in the style of hip-hop gangsters, the four boys of the Serial Killer "posse" often endearingly call each other "négro" or "néger", while arrogantly referring to women as "putes" (meaning "bitches", "sluts" or "whores"). They also sometimes curse, shouting the word "putain" or saying phraes containing it in various contexts. Plenty of other curse words are uttered as well, like "merde" (meaning "shit"), even in literal reference to feces.
In one scene, a young boy says, "Putain. Nique sa mère, le flingue on va à la teuf." In another scene, a young boy says to a teenage boy, "T'as voulu test avec mon posse, pute de merde!"
A teenage boy says, "Le pédé a une vraie meuf." Which contains a noun that may be derogatory toward homosexual males, like in the same way as "faggot".
From French to English, the translations in the form of subtitles or dubbing, for this movie, may provide the word "fuck" as the interpretation of some instances of the word "putain".