According to ESRB, this game contains: Blood, Drug Reference, Intense Violence, Strong Language

Parents should under no circumstances allow their children anywhere near this game. The tale of vicious murderers who kill innocent people to achieve their goals, K&L is as morally questionable a game as you're likely to find. Sure, the story throws in a few random nods at redemption, like having the main characters occasionally feel bad about all the people they're killing, but that doesn't change the central awfulness of nearly every bloody murder that takes place over the course of the game.
Fans of Noir and Crime cinema take note, this is the closest approximation to Heat you're likely to get in a videogame. So if you're dying to play that famous bank robbery, this is your best chance. Unfortunately, the game's fractured, often ridiculous storytelling keeps the plot from reaching the level of a decent film, and the random, senseless slaughter is a lot harder to take when you're the one causing it, rather than just a passive observer.
Co-op loving gamers will want to pick up K&L not just because the main game is centered around a co-op mode, but because the multiplayer minigame is entirely co-op focused. Rather than simple deathmatching or objective-based play, the game, called 'Fragile Alliance' allows teams of players to rob various locations, then attempt to escape as the computer-controlled police hunt them down. Although it suffers from the same control issues as the main game, overall it's a breath of fresh air in an otherwise frustrating title.
Deaf and Hard of Hearing gamers will be mostly fine. Dialogue is subtitled and directions are given with an onscreen radar. Sadly there aren't full captions, so the whens and where of gunfire will likely be a mystery until you're actually being shot. Luckily, the game features progressive, regenerating health, so you won't be at too much of a disadvantage.