도대체 is an intensifier adverb for a question or negative sentence, similar to "(what) on earth", "(how) in the world", "(where) the devil", etc. It expresses that you really want to know something but have no clue, or when making a sharp negative comment. - 얘는 도대체 왜 안 올까? = What the hell is keeping him? - 얘는 도대체 공부를 안 한다 = He just won't study at all. - 너는 도대체 왜 그 모양이냐? = Why on earth are you so messed up? (rhetorical. => You're hopelessly messed up.) - 지민 당신은 도대체 어디까지 갈 생각입니까? = Jimin, just how far are you going to go? (rhetorical. => Jimin, it looks like there just is no stopping you.).

도대체 in the sentence means "wow" with admiration, wonder, awe. 지민 당신은 도대체 어디까지 갈 생각입니까? Wow! Jimin, how far are you going to go?