What's the shortest amount of time between a character being introduced and built up, to them dying and getting offed?

I love catching it when it happens, sometimes you could see a character walking around with a death flag taped to their backs, other times you couldn't see it coming. The latter is my favourite, when a character has to be offed because the actor's contract expired, or the show handlers decided to cut the run time short and speed up an arc etc.

I can't think of any specific example at the moment, but the classic version of this is when a character talks about their family and what they're gonna do when this is all over and you learn instantly that they're building this dude up to kill him for shock value a couple scenes later.