LFK
LFK has 2 meanings
Let's french kiss
LFK is an acronym that stands for "let's French kiss", which is a more ambitious form of KM that involves some tongue in the kissing. It is often used in online chat rooms.
LFK is a very forward acronym that is commonly used by desperate guys online. However, it is sometimes used in a joking manner to show affection to another person.
Example
You seem nice, LFK. (Though that may be moving a little fast.)
Take the pop culture acronym challenge
LFK is an acronym used in the gaming community that stands for "Let's freaking Kompete" or the vulgar "Let's f****** Kompete." It is similar to LFG but replaces "go" with "Kompete," a free sports game for Xbox, Playstation, PC, iOS, and Android.
Since most people aren't familiar with LFK or Kompete, LFK is a niche acronym that mostly Kompete gamers use. Typically, gamers use LFK to pump each other up before playing Kompete. Or, they may use it to rally others to stop whatever they are doing to go play.