will kill me날 is the informal contracted form of 나를, meaning “me.” Depending on context and intonation, this can be a serious threat, a worried question, or an exaggerated complaint. 거야 expresses a future expectation or intention.
KO: 이 속도로 운전하면 사고가 나서 날 죽일 거야!
EN: If you keep driving this fast, you're going to get me killed!