KoS

KoS, K.o.S., abbrev., phrase, n., adj., EverQuest-ism 1. abbrev. for "Kill on Sight." 
2. On EverQuest and other MMORPGs, refers to a character having a faction with given NPCs so bad that they will aggro on the character as soon as they see him.
Ex: I can't go to Oggok; I'm KoS to the city guards. [GJ1]