-kys in sports games or fps games often used in short for "keep your score" when worse players try to complain about your own gameplay.
"you're terrible you only have 3 kills"
"You have none dude how about you kys before you worry about mine"
It doesnt mean keep yourself safe, it means kill yourself, get it right dumbfucks
"You're so annoying, y'know what? kys."