600k means 600 killers. 600 is a Black Disciples set located in Chicago, Illinois. Enemies of the 600 gang often add a k add the end of 600 to let others know that they are enemies of 600. It is very common for gang members to add a K at the end of their enemies’ gang names; other instances include 300K, BDK, GDK, among others.
Numerous artists have claimed 600k in their songs including TTBNez and Lil Jay whom is from St Lawrence in an Insane Gangster Disciples click. In his song “Who the Fuck is Dude” Lil Jay says “F*ck 600, I’m STL, so it’s f*ck 600” “BDK, 600K”.