In a kill game it becomes a kill pot once someone has won a pot back to back. So in 1/2 Kill say you won 2 pots in a row SB and BB posts the $1 and $2 blinds and you post a $4 wherever you are sitting and its kind of like a straddle and you still have an option. But say you won the pot again it only doubles once so you’d just have to post the $4 “kill blind” again.
You tend to see kill variants for LHE rather than NLHE though.