KYS

it means Kill Your Self

When someone Fuzes the hostage in rainbowsix siege

fuze:*detonates clustercharge*
announcer:*hostage has been killed, friendly mission failed*
team: OMG KYS

when a level 230 platinum 3 plays casual on rainbow six siege
everyone: OMG KYS NOOB GO RANKED
he:nononono kys yall, yall got reported